People.  The essential point to every story.  These are the characters in the Harry Potter series by J.K. Rowling.  In little particular order:

Harry Potter:  A young, slightly daring boy.  The hero of our story.  He is currently 13 years old, in his 3rd year at Hogwarts.  At infancy, his parents were murdered by a very powerful dark lord, but he was unable to kill Harry, leaving him with a small lightening-shaped scar on his forehead.  Harry, now an orphan, is left to be raised by his extremely preteniousm pure-Muggle aunt and uncle, the Dursleys.  At 11, Harry learns of his identity as a wizard.  He begins attendance to Hogwarts School of Witchcraft and Wizardry in England, around London.  There, he is Seeker of the Gryffindor Quidditch team.  He also defeats Voldemort, the wizard who killed his parents twice, and saves his godfather from certain death.  His best friends are Ron Weasley and Hermione Granger.

Ron Weasley:  A young, very red-haired boy.  Best friend of Harry Potter, Ron is slightly overshadowed by him and his brothers.  He is the youngest of six boys and has one younger sister, named Ginny.  He is almost as brave as Harry, but not quite.  He has gotten past McGonagall's giant chess set, an extraordinary feat.  He also helped Harry in the Chamber of Secrets.  Ron comes from a long line of wizards, but unfortunately, his family is very poor.

Hermione Granger: A young, intellectual, brown-bushy headed girl.  Hermione is best known for her intelligence.  She comes from a Muggle family, but does not let that defeat her.  She is top of her class, and always receives the best marks.  Hermione's parents are both dentists.  She is also brave and extremely logical.  Unknown t o the world, she helped free the wrongfully convicted godfather of Harry, Sirius Black.

Professor Albus Dumbledore: The Headmaster at Hogwarts.  Dumbledore is the one who arranged for Harry to live with the Dursleys.  He also acts as a sort of guardian to Harry during his life at Hogwarts.  Dumbledore has many time provided Harry with information ahead of time to help him battle evil.  Dumbledore is a very wise and very powerful wizard, said to be the only one Voldemort is afraid of.  He also gives Harry much leeway in his time at Hogwarts. A handwriting sample: 
 

Professor Minerva McGonagall:  The Deputy Headmistress at Hogwarts.  McGonagall is not a woman to cross.  She is described as a tall, black-haired witch with a stern face.  She is also very powerful.  She is one of the seven known Animagi in the world.  McGonagall teaches Transfiguration at Hogwarts and is head of Gryffindor.  She also played a roll in the placing of Harry after the murder of his parents.  She is a trusted and valued friend of Dumbledore.

Rubeus Hagrid: Hagrid is a very large, burly man.  He is the keeper of the keys at Hogwarts.  Wrongfully accused of opening the Chamber of Secrets, Hagrid was expelled from Hogwarts and his wand snapped.  Now, his wand resides in his large pink umbrella which is always at his side.  Hagrid is very good with animals and is the teacher of Care of Magical Creatures at Hogwarts.  He has an odd sense of humor, but is extremely devoted to Dumbledore.  Hagrid transported Harry to the Dursley's after his parents' death.  He also assisted Harry when Harry first learned his true identity.

Draco Malfoy: An evil boy.  Malfoy is Harry's most hateful enemy of his own age.  Malfor, a Slytherin, comes from an old, rich wizarding family.  His family used to be devoted to Voldemort and probably still hold alliance to him.  Malfoy is Slytherin's Seeker, though not by skill.  His father, Lucius Malfoy, holds a high position of influence at the Ministry of Magic.  Malfoy is backed up by his two cronies, Crabbe and Goyle.

Percy Weasley: Percy Weasley was Head Boy at Hogwarts.  He is Ron's older brother.  He has just graduated Hogwarts, and has fiery red hair like the rest of his family.  Percy is a bit pretentious; he always is very authoritative, though he did lose control when Gryffindor won the Quidditch Cup.  He was a prefect for Gryffindor before he became Head Boy.  Percy's aspirations include working at the Ministry of Magic.  He is also very intellectual.  His girlfriend is Penelope Clearwater, a Ravenclaw prefect (who also has graduated)

Fred and George Weasley: I hate to group them together as one, but as described, they have no defining characteristics.  Fred and George provide extensive comic relief throughout the books.  The are the next-in-line after Percy, and are about to become sixth-years at Hogwarts.  Known for their extremely prankish attitude, you can't help but love them.  Fred and George are the previous possessors of the Maurader's Map.  They are extremely witty and creative with decent marks at Hogwarts.  They, in no way, want to become leaders like Percy.  They are also the Beaters on Gryffindor's Quidditch team, because they are like a pair of human Bludgers themselves.

Professor Severus Snape: An extreme adversary of Harry Potter.  Snape holds a grudge against Harry because his father tried to pull a very bad prank on him, but ended up saving his life, so Snape would never harm Harry.  Just make life miserable.  Snape is the Potions teacher at Hogwarts, though it is rumored he'd rather be teaching Defense Against the Dark Arts, even though he's very good at what he does.  Snape is described as a thin man with sallow skin, a hooked nose and greasy, shoulder-length hair.  Snape is the head of Slytherin.

Neville Longbottom: A nervous round-faced boy.  Neville is a fellow Gryffindor of Harry's.  He doesn't make very good marks and is extremely hated by Professor Snape.  He is very scared of Snape, also.  Neville is frequently used by Draco Malfoy for "practice".  Neville owns a small toad called "Trevor" which always seems to be escaping.  He loses things frequently and is has recently been punished for leav ing a week's worth of passwords laying around for Sirius Black to steal.

Sirius Black: (Padfoot)  Best friend of James Potter.  Godfather to Harry.  Wrongfully accused of killing thirteen Muggles.  Served eleven years at Azkaban until escape.  Rescued by Harry and Hermione and now lives in hiding.  He is also best friends with Professor Lupin and wants to kill Peter Pettigrew.  Sirius Black is a thin man with long stringy hair.  He is capable of transforming in to a large black dog.

Professor Lupin: (Moony) Former Defense Against the Dark Arts teacher.  Quite well at  it, actually.  Lupin is also a werewolf.  Dumbledore knew this, and didn't care.  Snape knew and tried to give the students clues so they would find out and get him fired.  It came out that he was a werewolf after the escapade with Sirius Black and Peter Pettigrew.  Lupin resigned after this.  Best friends with Black and James Potter.

Peter Pettigrew: (Wormtail and Scabbers) Ron's rat for eleven years.  An Animagi.  Peter is the true murderer of the thirteen Muggles Sirius Black is accused of killing.  He also gave James and Liliy Potter away to Voldemort, giving him access to kill them.  Not killed by Harry for a later purpose.  Former friend of Lupin, Black, and James Potter.

James and Lily Potter: Harry's parents.  Lily died trying to save Harry from Voldemort.  James tried to fight him off while Lily escaped with young Harry, but it didn't work.  They were both betrayed by Peter Pettigrew, who was their secret-keeper.  Harry looks just like James, with wild, black hair and glasses.  Harry also has Lily's eyes.  Apparently, they were very powerful wizards, which is why Voldemort was after them.
 

Ginny Weasley:  A red-haired (just like her brothers) girl.  She is the youngest Weasley.  She has a sort-of crush on Harry and becomes very shy around him.  She recently caused havoc by opening the Chamber of Secrets, but was rescued by Ron and Harry.  Ginny is one year younger than Ron and Harry.  She is the only girl of her family.

Professor Flitwick: A small squeaky man.  Professor Flitwick is the Charms teacher at Hogwarts.  He is also the head of Ravenclaw.

Professor Sibyll Trelawney: A short, dark haired witch.  Professor Trelawney is the teacher of Divination at Hogwarts.  She is described as very thin; her large glasses magnify her eyes to several time their natural size, and she is draped in a gauzy spangled shawl.
 

Professor Sprout: A squat little witch who wears a patched hat over her flyaway hair.  Professor Sprout teaches Herbology at Hogwarts.

Professor Binns: Professor Binns is an old ghost who just died one day, sitting in a chair.  He teaches a very boring History of Magic at Hogwarts.

Oliver Wood: Former captain of Gryffindor Quidditch team (also the Keeper).  His life, he always wanted to win the Cup, and now he's done it.  Wood is known to push his team to the extreme to excel, including early morning practices.

Dean Thomas: A fellow Gryffindor of Harry's who comes from a Muggle family.  He does well at Hogwarts and is a friend of Harry's and Ron's.  His favors soccer and his favorite team is the West Ham soccer team.

Seamus Finnigan: A fellow Gryffindor.  He has dusty brown hair.

Parvati Patil: A fellow Gryffindor.  Frequents Professor Trelawney often.  Good friend of Lavendar Brown.

Lavendar Brown: A fellow Gryffindor.  Same as above.

Angelina Johnson: Gryffindor Chaser.  Year unknown.

Katie Bell: Gryffindor Chaser: Year unknown.

Alicia Spinnet: Gryffindor Chaser. Year unknown.

Marcus Flint: Former Slytherin captain of Quidditch.  Had to repeat his sixth-year.  Big, burly will resort to any means to win.

Professor Quirrel: Former teacher of the Defense Against the Dark Arts.  Servant to Lord Voldemort.  Was killed when Harry defeated Voldemort in the Sorcerer's Stone.
 
 

Professor Gilderoy Lockhart: A talk and no proof.  Former Professor of the Defense Against the Dark Arts.  Lost his memory in the Chamber of Secrets.  Complete git.  He wrote several books which turn out to be fake because he can't even recapture pixies.
 

Argus Filch: A Squib.  Head facilitator for Hogwarts.  Keeps everyone in line, also cleans.  Assisted b y Mrs. Norris, his scrawny black cat.

Justin Finch-Fletchley: A Hufflepuff.  Though Harry was trying to kill him.  Petrified by the basilisk.

Colin Creevy: Great admirer of Harry.  Completely absorbed with him in the second book.  Even took pictures and wanted them signed.  Also petrified.

Penelope Clearwater: Former Ravenclaw prefect and Percy Weasley's girlfriend.  Also petrified.

Nearly Headless Nick: Gryffindor House ghost.  Whacked firty-five times in the head witha dull ax.  Half inch of skin holds his head on.  Helpful to first years.

The Grey Lady: Ravenclaw house ghost.

The Fat Friar: Very jovial.  Hufflepuff house ghost.

The Bloody Baron: Slytherin house ghost.  Very brooding and secretive.  Only one known who can control Peeves.

Peeves: The poltergeist of Hogwarts.  Very mischieveious.  Helps neither students nor teachers.  Just likes causing trouble.

Moaning Murtle: Killed by the basilisk 50 years ago.  A grubby, insecure girl who always seems to be crying and thinks everyone is after her.  Haunts the girls' bathroom.

Bill Weasley: Not really a character, but another Weasley brother.  Bill works in Egypt at Gringotts.  He was Head Boy at Hogwarts.

Charlie Weasley: Another Weasley brother.  Works in Romania with dragons.  Captain of Gryffindor Quidditch and won the Quidditch cup when he was at Hogwarts.