Just like with homeowner's insurance, auto insurance comes in a variety of flavors.  The three main components are liability, collision and comprehensive (aka "other than collision").  Liability pays for property damage and injuries to other parties when you are at fault.  Collision pays for damage to your car (minus your deductible); and Comprehensive pays for things such as theft, fire, vandalism and other perils.  "Limits" are the extent to which the insurance carrier will pay for damage.  "Split Limits" (ex: 100/300/100) are amounts that the carrier will pay for bodily injury per person and per occurrence, and property damage per occurrence.  Combined Single Limit ("CSL") is the amount that the insurance carrier will pay for all bodily injury and property damage combined.  Common amounts of CSL coverage are $300,000 or $500,000.

Uninsured and Under-insured Motorist coverage (UM and UIM) covers you if someone collides with you and it's their fault and they don't have insurance or do not have enough insurance to pay for all bodily injury or damage to your car.