A drainage basin is the area of land drained by a river and its tributaries. All precipitation falling within this area eventually flows into the same river system. The boundary of a drainage basin is known as a watershed or divide, which separates it from neighboring basins. Drainage basins vary greatly in size, from small local streams to vast systems covering multiple countries. They are important for water resource management, as human activities within a basin directly affect water quality and availability. Proper understanding of drainage basins helps in flood control and sustainable land use planning.