What is a delta?

A river delta is a land form created at the mouth (or source) of the river, from the disposition of the sediment the river has carried, and dropped when the river flows into the mediterranean sea.Over long amounts of time the deposition builds up to become a river delta.

River deltas form when a river carrying sediment reaches  a body of standing water like a ocean, lake etc. It is considered highly fertile land, As you can see on the diagram the area of the delta is green, unlike the rest of the country. The Egyptians have been farming on the delta for thousands of years. 

This is the river Nile delta.
 It is formed at the mouth of the river Nile.

The Nile Delta,is formed in northern Egypt,where the mouth of the river is. It  is one of the worlds largest river deltas, at 160 km long. And it covers over 240km of coast line.