An exclave is a term used in geography to describe a country or territory that belongs to another country but is surrounded by countries to which it has no belonging or affinity. It is usually at least partially separated from the main country, state, or political region. This is often used when describing political geography, focusing on the boundaries, of each country as defined by political rule. Borders on political maps generally represent a country organized under one government, or states, counties and cities belonging to a country. Yet the borders of an exclave are not connected to the country to which it belongs.
The term exclave gets confusing when compared to the term enclave. A country that surrounds another country may consider the interior country an enclave. If the country being surrounded does not have political affinity or does not belong to another country, then it is solely an enclave. For example, Vatican City is an enclave of Rome. Vatican City has its own government, independent from Rome and Italy. It is not bound by the rules of Rome, and in many cases not by the rules of Italy.
Lesotho is another enclave example. It is an independent kingdom, landlocked and completed surrounded by South Africa. It doesn’t in any way belong to South Africa and is its own nation, recognized as such internationally.
An exclave can be an enclave. Usually the distinction of a true exclave from enclave is that the exclave has some access, like river or sea access to the country to which it belongs. Alternately, it may be connected to its ruling country by a minute border. For example, French Guiana in South America shares political affinity with France but is not physically connected to it. Surinam and Brazil, and also the Atlantic Ocean border it. This gives France a way to access it without necessarily crossing into other countries to do so.
Alaska is another example of an exclave. It is separated from the US and shares boundaries with Canada. Again it is accessible by sea with the boundaries of the Arctic and Pacific Oceans and the Bering Sea.
A country can be both an exclave and enclave. But not all are. In the case of Lesotho, for instance, the country doesn’t belong to anything but itself. It is therefore an enclave but not an exclave. Sometimes the exclave merely separates part of a country or territory. For example part of Fulton County in Kentucky is separated from the rest of Kentucky State, and extends into Tennessee.
Other parts of land can be considered practical exclaves because although they are not considered wholly separated from the land to which they politically belong, the geography of the area makes them impassible except by entering foreign territory. Parts of the Republic of Ireland can only be accessed by crossing into Northern Ireland for instance.