Saiyans
This is a very strong and vile race.The saiyans lived on the Planet Vegeta, which was later destroyed by Frieza. Saiyans have extraordinairy power, and can transform into a Super Saiyan and further.Their hair color is usually black, and they have black eyes and a tail.

Super Saiyans
A saiyan can transform into a Super Saiyan if his power is big enough, and if some emotional stuff happens. The Super Saiyan's power and speed increase very much, and he gets green eyes and gold hair that stands up.

Ultra Super Saiyan
In this stage the power increases dramatically. The hair of a Saiyan gets pointy, standing up hair.The only desadvantage of this stage is that the muscle are so big, that the speed decreases greatly.Trunks, e.g was much stronger than Cell, but he was so slow that Cell could easily beat him up.Goku also became a Ultra Super Saiyan, but he could change something about it.

Super Saiyan 2
In this stge, the power as well as the speed increases dramatically.The hair doesn't fall down, but stands up high.Also, a lighting bolt surrounds the KI of the Saiyan. Gohan was the first to reach this stage, in the Cell saga. Cell was creating children, and that children beat up all of the Z-warriors. Then, he killed Android 16. This triggered Gohan to go ssj2.

Super Saiyan 3
A Super Saiyan 3 is the strongest level in Dbz. his hair falls down and gets very long, almost to the ground.The Saiyan is so fast, that his speed is unfollowable. You only see zips if he moves. His strength is also overwhelming.The muscles are also very big. The only disadvantage of this level is, that it costs very much energy to transform, and you can't stay in this form very long. The only ones who have reached this are Goku and Gotenks. Vegeta didn't.

Super Saiyan 4
This level can only be reached through the Golden Oozaru Form, which can only be achieved with a tail. The saiyan becomes very, very strong and the hair turns black again. A red fur covers the body except for the front. Also, a long, red tail is grown again. Goku wasthe first to reach it, when he saw Pan cry. Vegeta couldn't go Super saiyan 4, becaus he didn't have a tail. But Bulma build a machine called Brute ray, and this made Vegeta's tail grow again. then he went to the planet Plant and went Golden Oozaru, and after that Super Saiyan 4.

Oozaru
This level is only used at the beginning of Dbz. When a saiyan looks at the full moon, and he still has his tail, he transforms into a giant monkey.His power is ten times as big as before. Gohan went Oozaru a few times, and then Piccolo cut off his tail. After that, once more he goes Oozaru when Vegeta fakes a moon. When Gohan went Oozaru, he could't control himself. Vegeta could, he trained on that.

Golden Oozaru
This level is only reached in DBGT.When a Saiyan looks at the full moon on Planet Planet, he transforms into Golden Oozaru. His fur is gold, and his power is 15 times as big as before.

Nameks
Nameks are very strong and friendly. They are green and have pointy ears. Piccolo and Kami are an example of a Namek. There are two types of Nameks: Fighters and Healers. Fighters can fight, such as Piccolo, and healers have the ability to heal, such as Dende.

Earthlings
earthlings aren't very strong. They can be strong after training a lot, like Tien, but none of them has the power such as that of a Saiyan. The strongest know Earth warriors are Tien, Krillin and Yamcha.

Challenger
The challenger race is the strongest race aftre Saiyans. Challengers are very powerful, and can transform a couple of times.They need a lot of time to transform. Freeza, King Cold, Kooler and all the other brothers of Freeza are Challengers.

Arlians
Arlians are just like bugs. they aren't very strong,and are chickens.All of them were killed by Vegeta

Yardrats
This are the people of Yardrat. they are friendly and taught Goku the instant transmission. They also gave him weird clothes, that was the fashion there. further there is nothing known more about the Yardrats.

Androids
Androids are half human, half robot. Their creator is Doctor Gero, he wants to kill Goku. And android isn't evil from nature, but it is changed. Android 18 becomes a partof the Z-gang and marries Krillin, and they get a kid, named Marron.

Makios
These are the creatures that live on the Makio Star.They are very evil and can become stronger, if their homeplanet is close enough.Garlic Junior isan example of a Makio.