Sovereign states (or countries) generally appear on the map as solid, contiguous blocks of territory, and they are certainly conceptualized as such. But exceptions abound. Many countries, for example, have separates “annexes” located at some distance, technically known as exclaves (think of Alaska). Bits of territory within the boundaries of one state that belong to another are defined as enclaves. Entire countries can be enclaved within another sovereign state, such as Lesotho in South Africa or San Marino in Italy.
Enclaves and exclaves are generally fairly straightforward, but they can become quite intricate. A counter-enclave, for example, is an enclave within an enclave. Thus the village of Nawha is part of the United Arab Emirates, yet is wholly surrounded by a part of Oman called Madha, yet Madha itself is wholly surrounded by territory belonging to the United Arab Emirates (see map). As Evgeny Vinokurov shows in his A Theory of Enclaves (2007, Lexington Books), this pattern can be taken one more step. Thus Dahala-Khagrabari is a sliver of Indian territory (a jute field, more or less) that is surrounded by Bangladeshi territory that is surrounded by Indian territory that is surrounded by Bangladeshi territory: a counter-counter-enclave, in other words. Must make immigration control rather interesting.