A geographical feature known as a delta is formed where a river meets a body of water, such as an ocean or a lake, creating a landform that is usually triangular or fan-shaped. The sediment carried by the river is deposited at its mouth, leading to the formation of new land. Deltas are important ecological zones, providing habitats for diverse wildlife and acting as crucial regions for agriculture due to nutrient-rich soils. Famous examples include the Nile Delta in Egypt and the Mississippi River Delta in the United States.