An enclave is a separate space or group within a larger one. Imagine an enclave as a cave carved out of a big mountain. All of the bears live in the cave or enclave, while the people live on the mountainside.
Groups of like people often form an enclave within a country or region. There is probably an enclave of Africans, Cubans, Russians, or other ethnic group in or near your hometown. It isn't usually enclosed, but it's a place where people of the same background gather and live together, such as a Chinatown or a Little Budapest. An enclave of a country may have boundaries, making it clear that it's a distinct part — and sometimes under separate government — from the larger territory it's within.