A canton is a type of administrative division of a country. In general, cantons are relatively small in terms of area and population when compared to other administrative divisions such as counties, departments or provinces. Internationally the best-known cantons, and the most politically important, are those of Switzerland. As the constituents of the Swiss Confederation, theoretically (and historically) the Swiss cantons are semi-sovereign states.
The term is derived from the French word canton meaning corner or district (from which "Cantonment" is also derived).
More information on the Wikipedia page [1].