Modifications can mean something as little as adding alloy wheels or a spoiler, or something as extravagant a turbo conversion. This can add value, increase theft risk, make it more difficult to find replacement parts and mean that the driver is categorised as higher risk. This is why insurance providers term modified cars or vans as non-standard vehicles, and the insurance premiums are higher.
I was with Liberty Mutual for about 15 years and was very satisfied with their prices and service, although I never filed a claim. When I retired and moved from California to Florida, my auto rate went up a ridiculous amount, to almost $10,000 a year even though I had no accidents and one minor moving violation in the last ten years. On top of that, Liberty Mutual screwed up my umbrella policy and told me it was “unenforceable,” whatever that means, but I had to pay for the policy anyway up to the time I canceled and switched to Progressive, which cost about one third the cost of Liberty Mutual for an identical policy. Even good companies change over time.
When your vehicle is damaged in an accident, collision insurance is an optional coverage that pays the cost of repairing or replacing it, minus the amount of your deductible. Collisions can involve another vehicle or an object, like a guardrail or a tree. If you lease or finance your vehicle, you may be required by your lender to purchase collision insurance coverage.
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.