There are 2 types of liability policies you can choose from.  These include the single limit policy and the combined limit policy.

Single Limit Policy:

The first and most popular is the single limit policy. 15/30/10 is a single limit policy; liability limits.  The 15 represents in the thousands how much your insurer will pay out for one person’s injuries if you hit them in an auto accident and are at fault for the collision. The “30” represents in thousands the total amount your Insurer will pay for all bodily injury.  The 10 represents $10,000 of property damage (PD) paid out for damages to the car you hit.

Combined Limit Policy:

Lets say you select a (CL) Combined limit of 40,000.  If 15/30/10 is the state minimum required, than 40,000 is the state minimum required “combined limit”. 30 + 10 = 40.  This 40,000 can be distributed a variety of ways.  If you hit a parked BMW and cause $20,000 of damage, you single limits policy will only pay up to $10,000 for the damage you caused.  With a $40,000 (combined limit policy) all damages you caused to this parked BMW are covered. 

Typically, Combined Limit policies are more expensive than Single limits policies for the well known fact that they will better protect the Insured financially.  Note that Liability requirements will vary from state to state.