-Goku First reaches super sayian level one in the Freeza saga when Freeza kills Krillin and Goku becomes really angry and goes beserk.
-When a sayian reaches this level his power level and muscle increases a lot making him really strong and powerful.
-The hair becomes gold and it grows a bit longer.
::Super Sayian Level Two::
-Goku had reached this level in Movie 4 when he was fighting Cooler.
-When someone reaches this level his power level rises extremely high and muscle mass grows much bigger
-In this stage the hair gets longer and thicker and sometimes a small zap of lighting pass across the sayian
:::Super Sayian Level Three:::
-This is the ultimate level of Super Sayian Form. Goku had reached this stage during the Majin Buu saga.
-Then someone reaches this level his power level becomes over 37 million and his hair really grows longer and becomes more goldish.
::::Super Sayian Level 4::::
-Goku and Vegeta reached this level in Dragonball GT. It doesn't look like a sayian form but it is still more powerfull than the other forms.
-In this form, your hair goes black and you grow red fur around your upper body. Though Goku doen't have a tail, in this from he grows one automaticly for some reason.
-In this form he can do some special attacks like 10x Kamehameha and Ultimate Kahmehameha.