Reinsurance

What Does Reinsurance Mean?
The practice of insurers transferring portions of risk portfolios to other parties by some form of agreement in order to reduce the likelihood of having to pay a large obligation resulting from an insurance claim. The intent of reinsurance is for an insurance company to reduce the risks associated with underwritten policies by spreading risks across alternative institutions.

Also known as "insurance for insurers" or "stop-loss insurance".

Investopedia explains Reinsurance
Overall, the reinsurance company receives pieces of a larger potential obligation in exchange for some of the money the original insurer received to accept the obligation.

The party that diversifies its insurance portfolio is known as the ceding party. The party that accepts a portion of the potential obligation in exchange for a share of the insurance premium is known as the reinsurer.