A drainage basin is any area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water.

What is catchment area of a river?

A catchment is an area of land where water collects when it rains, often bounded by hills. As the water flows over the landscape it finds its way into streams and down into the soil, eventually feeding the river.

What is the difference between a river and a catchment?

"A catchment is an area of land from which water drains into a river. Every part of the earth's land surface is part of a catchment. Neighbouring catchments are divided by watersheds, and rivers are arranged within catchments in drainage patterns."