This is a sorta weird anime for me to explain. I liked it, but it's just too darn confusing to know what's actually going on until the 3rd time you watch it. I'll try to explain it the best I can....
The plot is sorta religiously based. I really can't explain this-sorry. I know it's about NERV secretely keep Adam-the First Angel-from uniting with an angel; if they do so, another impact could occur. He was the cause of the Second Impact that destroyed almost all of the earth's inhabitants. Evangelions are the only ones who can stop that. Evangelions can stop angels from coming near Adam. They are half god/ halfhuman. It's something like this: man found god, and he got mad as a monkey; so god punished man by the second impact. then god disappeared, so man tried to make god-adam. and man made themselves to evas to do that. That info is found out near the end of the series.
There are three main Eva pilots in this story-Shinji Ikari(3rd child), Asuka Langley Soryu (3/4 German,1/4 Japanese(2nd child)), and Rei Ayanami(4th child). They're main mission is to destroy the angels when they attack the city.
Misato katsuragi is the NERV Operations Chief. She adopts Shinji as her little brother-sorta-after he moves in. The reason she joined NERV ther first place was that she hated the Angels that caused the Second Impact that killed her father, who tried to save her life. Ritsuko Agaki is Misato's friend-their friendship goes all the way from school. Ryouji Kaji is a friend of both Misato's and Ritsuko's-but it seems that Misato and him had a relationship before. She later tells him that the only reason she broke up with him was that he reminded her of her father.
Shinji's father-Gendo Ikari- is the NERV supreme commander. He seems, though, that he is doing another mission and is rarely seen in the main deck. He's had a bad relationship with his son, esp. eversince Yui-his wife- died when Shinji was only four.
This series was confusing, but hey, it's good-the drawings were good! The actions sequenses were pretty good, too..it's just that the story line was sorta confusing to me. But I do recommend this anime.