Excess liability insurance, increases your total limits of insurance beyond those of your primary liability policies, such as general liability and automobile liability. For example, your primary CGL policy has a $5 million dollar limit. In order to have a $10 million total limit, you can purchase another $5 million dollar Excess Liability to stack on top of your primary  policy.

Umbrella Liability policies typically provide broader coverage than the primary terms and conditions and can sit above multiple primary policies such as CGL and Automobile.