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.
Auto insurance premiums depend on the insured party's driving record. A record free of accidents or serious traffic violations typically results in a lower premium. Drivers with histories of accidents or serious traffic violations may pay higher premiums. Likewise, because mature drivers tend to have fewer accidents than less-experienced drivers, insurers typically charge more for drivers below age 25.