The main difference between collision and comprehensive coverage comes down to the question of what the driver controls. Collision insurance will cover events within a motorist's control or when another vehicle collides with your car. Comprehensive coverage generally falls under "acts of God or nature," or things that are typically out of your control when driving. These can include events such as a spooked deer, a heavy hailstorm, or a carjacking.
Comprehensive car insurance covers damages from an "act of God," or events that are not caused by a car driving into something else. An "act of God" can include things like damage from a heavy tree branch falling on your car. Since you have no control over when or why a tree branch would fall on your car, this kind of accident would be covered under your comprehensive policy.
This coverage reimburses you for the cost of your rental car if your insured vehicle is in the shop or is unavailable due to an accident. You need to have comprehensive and collision on your policy in order to add rental car coverage. In certain states, Esurance offers CarMatch Rental Coverage®, which covers the rental cost of a vehicle comparable in size and body type to your regular ride.