Be sure to check the Techniques section to see which skills your chosen race begins with.
Saiyan
They first arrived on the Planet Plant in 550AD and eventually took over the whole planet, renaming it Vegeta. They then encountered Frieza, who employed them to wipe planets of their life before being sold. Fearing they would one day overthrow him, Frieza destroyed them all along with the planet, leaving only a handful of survivors.
Changeling
This is the race to which Frieza, Cooler and King Cold belong. Not much is known of their origins. All that is known is that all changelings possess the ability to transform & not just once but several times. Doing so greatly increases their power. As a side note, I'd like to point out that the term "Changelings" is never actually said The name in actuality is just something fans made up for easy discussion somewhere between the mid-to-late 1990's.
Namekian
This race is first introduced to us when Goku fights Piccolo Daimao, who is a very old Namekian. But it isn't until the Saiyan Saga that Piccolo and Kami learn of their otherworldly origins. After Piccolo's death at Nappa's hands. Gohan, Krillin and Bulma depart to the Planet Namek, to gather the original Dragonballs to revive their friends. During this time all the Namekians are wiped out by Frieza and his men. They are eventually revived with the Earth's Dragonballs and sent to live on New Namek. All Namekians are asexual as they on snails and slugs.
Human
This, surprisingly, is the race to which we all belong. Humans inhabit the Planet Earth, and apart from a few individuals, most are comparatively weak along side people like the Saiyans and Namekians, because most of the race does not know anything about Ki manipulation.
Majin
A mystical creature made out of magical material, by an evil wizard or sorcerer. They can absorb other beings, and transform into things.
Android
This in an artificial race. Usually androids start out as another race, but are 'enhanced' with technology. All androids in the series are created by a doctor of some sort. They usually look just like normal people or can look very strange. They are immensely powerful.
Bio-Android
An android made from the DNA of several different warriors. They're usually weaker than Androids, but can make up for it by absorbing weaker beings and making themselves much stronger in order to absorb the necessary components to make themselves 'Perfect'. They usually have an almost insane level of obsession with this task.
Alien
This is the race that any unknown being belongs to. If a player wishes to create their own race, it's loosely based upon this classification. These beings can look like just about anything, with any kind of personality.
Demon
Usually evil creatures, who like to kill. They are generally creatures spawned from the netherworld, also known as Hell. They come in various colors, shapes, and sizes, with varying personalities.
Kaioshin
These creatures are even higher gods than the Kais. These gods watch over sectors of the universe, and one of the them is supreme god of the entire universe. They are immensely powerful, but not immortal, which is proved by Majin Buu, when he slaughters all but a handful of them.