A reinsurance agreement is a contractual agreement between an insurance company and a reinsurer where the reinsurer agrees to accept a portion of the risk associated with the insurance company's policies. Reinsurance allows insurance companies to spread their risk over several companies, reducing their exposure to catastrophic losses. In exchange for taking on this risk, the reinsurer charges the insurance company a fee or premium.

Reinsurance agreements can be structured as either proportional or non-proportional. In a proportional arrangement, the reinsurer takes on a portion of every policy issued by the insurer, typically a percentage of the premiums received. In a non-proportional agreement, the reinsurer covers a specified amount of losses resulting from a specific event or series of events, such as a natural disaster.

Reinsurance agreements can help insurance companies manage their risk and ensure they have adequate capital reserves to pay out claims. Reinsurers also gain access to larger markets and can receive a greater return on their investment than they would by investing in lower-risk securities.

Overall, reinsurance agreements play a vital role in the insurance industry, providing a means for insurers to manage risk and protect their policyholders.