Collision is commonly confused with comprehensive. They’re both optional coverages and pay to repair or replace your car (if it’s totaled). But they cover separate events. In short, collision covers accidents (other than with animals) and comprehensive covers events that are beyond your control such as theft, vandalism, hitting an animal, fire, glass breakage or an act of nature.
Think of it this way: Collision is colliding with another vehicle or object (other than animals). Comprehensive is all other events. Accidents with animals are covered by comprehensive (and not collision) because these accidents are considered out of your control. Also, you can’t add only collision. You have to add comprehensive first and then collision.