The term for a body of water surrounded by land is "lake." Lakes can vary greatly in size, depth, and water source. They can be formed through various geological processes, including glacial activity, tectonic movements, and volcanic activity. Lakes play an essential role in the ecosystem, providing habitats for diverse flora and fauna, serving as a water source for wildlife, and supporting recreational activities for humans. Notable examples include the Great Lakes in North America and Lake Baikal in Russia, which is recognized as the world's deepest and oldest freshwater lake.