No states require comprehensive coverage, but those who finance or lease their car will probably find that their lender or lessee requires it. Lenders and lessees are the official owners of the vehicle, so they want to make sure they're adequately protected in case of an incident. For the same reasons, you'll rarely be able to buy comprehensive insurance without also purchasing bodily injury liability and collision coverages.
There are two types of automobile third-party liability coverage. First, bodily injury liability covers costs resulting from injuries to a person. These injuries' costs could include expenses like hospital care, lost wages, and pain and suffering due to the accident. Second, property damage liability covers costs resulting from damages to or loss of property. Examples of property damage include the payment to replace landscaping and mailboxes, as well as compensation for loss of use of a structure.
Comprehensive insurance is commonly confused with collision. They both insure your car but cover different events. Collision covers car accidents, and comprehensive covers events out of your control. Think of it like this: Collision is colliding with something else (other than animals). Comprehensive is basically all other events. Accidents with animals are covered by comprehensive (and not collision) because these accidents are considered out of your control.