Collision: Covers damage to your car when your car hits, or is hit by, another vehicle or other object. This coverage is not required by a state, but if you have a loan or a lease, then the lien holder will require it.
Comprehensive: Covers your vehicle, and sometimes other vehicles you may be driving, for losses resulting from incidents other than collision. This coverage is not required by a state, but a lender may insist that you carry it until your loan is paid off.