Halfbreed Saiyans look like Saiyans, who look like Humans with monkey tails. Even though they are only part Saiyan, Halfbreeds are considerably more powerful than either pure Saiyans or pure Humans alone. Gohan turns Super Saiyan when he is only 11, Goten does so at 6 and Trunks at 7. Goku, a pure Saiyan, doesn't reach the level until he is well into adulthood, likewise with Vegeta, the prince of all Saiyans.
Like the Saiyans, a Halfbreed will turn into a giant Oozaru if it is exposed to moonlight while it has a tail. Chopping the tail off will stop this from happening.
wikipedia.org dumped 2003-03-17 with terodump