If something is in the way of a stream or river it has to go round it for example a tree or a rock.

After this first bend, the river hits the outside of the bend with more and more force to erode the river bank and enlarge the meander.

The eroded material is deposited on the inside of the bend >>> label this as the river beach.

This process continues >> The meander gets bigger and bigger until finally the river cuts through and meets at the other side.

This is an oxbow lake.