Nameks

A race that used to live on Planet Namek until Frieza blew their planet up while fighting Goku. They have green skin and according to one of their members (Dende) they do not eat they just need water in order to survive. They are usually ruled by the eldest Namek. They are a peaceful people. They fall into two categories: healers and fighters (these are very few since again they are very peaceful). They have the ability to regenerate their body parts if they are lost. They can can also stretch their arms for as long as they want ( this is a very primitive attack and is rarely used ). They are also the original creators of the Dragon balls. Piccolo, Kami, Nail, Dende, and Guru are all members of this race.

Saiyia-jins
This is a very powerful race. They are originally from Planet Vegeta. Long ago they used to work for Frieza, they captured planet for him and in return he spared their lives. They all have tails and when there is a full moon and they look at it they change into giant apes with enormous power. They can also turn into super Saiyia-jins with an ambition and/or lots of training. After that they can achieve SSJ2, SSJ3, and finally SSJ4 and some people say there is a form after that called Mystic form. They are by far the most powerful race. Goku, Gohan, Vegeta, Trunks, Brolli, Bardocks, Goten, Raditz, Nappa, Paragus, and lord Vegeta are all members of this race.

Earthlings
Well, you and me! They are the weakest of all the races in the DBZ universe. It is they that the other races either fight against or protect.

Changeling
They are a powerful race. There main source of energy comes from there transformations which they have four of.
They have a hard outer shell that protects them they have the ability to breathe in space. They are very few almost extinct but they live for a long time.

Androids
This race is made by Dr Gero. Not all of them are bad in fact Android 18 marries Krillen and Android 16 dies defending the Earth. The older models usually have the symbol of the red ribbon army inscripted on them somewhere. The strongest of the androids is cell (not pictured).