An Endowment policy is a life insurance contract designed to pay a lump sum after a specific term (on its 'maturity') or on death. Typical maturities are ten, fifteen or twenty years up to a certain age limit. Some policies also pay out in the case of critical illness.
Policies are typically traditional with-profits or unit-linked (including those with unitised with-profits funds).
Endowments can be cashed in early (or surrendered) and the holder then receives the surrender value which is determined by the insurance company depending on how long the policy has been running and how much has been paid into it.