The law varies by state and the differences are not subtle. I can only speak for Maryland or Pennsylvania, but since PA is different - I'll speak for just for Maryland.
There are several coverages:
Liability Bodily Injury: money we pay to other people if you are at fault for medical expenses, lost wages, or worse loss of life. This is listed per person and per occurance (ie $100k/$300k)
Liability Property Damage: money we pay to other people for their property that was also damaged (ie car, light pole, fiber optic nodule, bridge, etc.) This is the third figure in the liability section (ie $100k)
Medical (aka: no fault, personal injury protection, or PIP) This is considered primary coverage for medical costs incurred by you and your relatives inside your car as the result of an auto accident REGARDLESS of who was at fault, and will pay BEFORE your medical insurance carrier. In MD it's either $2500 (state minimum), $5000, or $10,000. YES, if someone hits you and you go the the ER and incur $2000 of bills YOUR own insurance will pay for it. That said it is not rateable - meaning not considered your fault and won't alone increase your rates. If you incur $100,000 of medical costs, your PIP pays out to the max and then the responsible party is on the hook for the remainder out of their Bodily Injury Liability coverage (see above).
Comprehensive (comp): Money we pay for YOUR vehicle in the event it is damaged by fire, vandalism, deer collision, theft, broken glass, tire slashings, etc.). This coverage is subject to a deductible of your choosing ($0 - $1000).
Collision: Money we pay for YOUR vehicle in the event it is damaged by YOU running into something (ie car, pole, curb, etc.). This coverage is also subject to a deductible you choose ($0 - $1000).
Emergency Road Service (ERS): Cheap coverage for lock-outs, tows, flat tires, dead batteries, etc. No deductible we pay the whole deal. In Maryland, if you have a flat tire and decide to change it yourself, there is a 75% chance you will be killed while doing it - call us. This is the AAA killer. We are $4.40 per year per car, they are....... more.
Rental Reimbursement: Money available to pay for or help you pay for the cost of a rental car in the event your car is in the repair shop as a result of your crashing or using your comp. coverage.
Uninsured/Underinsured Motorist: Money we have available to pay for damage to your and/or your vehicle in the event you're hit by a driver who doesn't have (he's going to jail) or has too little (Progressive?) insurance. Using this coverage invokes a state-mandated deductible $250 here in MD. So some schmuck hits you, totals your car, you go to the ER, and miss 6 months of work: We pay up to the coverage you selected (usually matches your liablity coverages (ie $100k/$300k/$100k). Sure it blows that you pay $250, but the alternative is that we pay nothing and you track Bubba down at the lottery store every Friday and get your money back $48 at a time. If you make alot of money, take that into account.
Those are the basics, I'll address questions as I am able to.
If you live in Maryland, I'd love have your business, and if you're a decent driver - It's likely to be a mutualistic symbiosis.
That said, if you are injured by a car your