A delta can be found where rivers empty into another body of water - such as a lake, an ocean, or a lagoon. They can also empty onto land, but this is much less common. Often, a delta is actually a wetland rather than a body of water or something of the kind. As a river gets closer to where it is going to empty out, it starts to move slower.
Sediment starts to collect at the bottom, and this creates the land that forms a delta. It also allows a river to branch out, breaking out of its single lane. It creates a branching effect. Often, it looks like a tree from space, or maybe from an ice vein that is expanding.
