A geographical feature known as a delta is formed at the mouth of a river, where it meets a body of water such as an ocean or sea. Deltas are characterized by sediment deposition, creating rich and fertile land suitable for agriculture. They often support diverse ecosystems and serve as important habitats for various fish and bird species. Notable examples include the Nile Delta in Egypt and the Mississippi Delta in the United States, both integral to their respective regions' economies and environments.