There are 4 different classes in CrazyBobs.
Classes dictate what Skills players can specialize in. The three Law Enforcement Classes (Police Officer, Police Technician and Medic) unfortunately don't give you an option and are locked to one specific skill each. Civilians however, can choose from 13 different skills ranging from Food Delivery to Rapist! The only way Law Enforcement can change their Skill is by changing their Skin at the Hospital.
The Civilian Class is identified by it's orange, yellow, green or white colored name on the skin selection screen while law enforcement classes are blue (and purple if they have requested backup).
Skins are sometimes also called classes. They are the bodies which players choose as their in-game avatar. Almost all Pedestrians from Grand Theft Auto San Andreas can be played as, with only some key storyline characters unavailable.