Oozaru- This is the form of when a saiyan that has a tail, looks at the full moon. During this form the saiyan grows to an enormous size and has a monkey like face, plus, is covered in a brown hair. Most saiyans when in this form are unable to control themselves and destroy everthing in their sights. This form is first seen in Dragonball when Goku turns into one.
Super Saiyan- This form is reached by being extremely angry or extremely obsessed. During this form the saiyans hair stands up, turns to a gold/blonde color as do the eye brows, then the eyes turn a greenish-blue. Strength is like doubled or tripled. This form is first reached by Goku while fighting Frieza on planet namek do to the death of both Piccolo and Krillin. However basically everybody reaches at least this form, except for the girl saiyans.