* Erosion is the process of wearing away and transporting material, like a river carving a canyon.

* Deposition is the process of dropping or settling that transported material.

Sandbars occur when a river or ocean current slows down. This slowing causes the current to lose energy, and it can no longer carry as much sediment. The sediment is then dropped, or deposited, forming a sandbar.

Here's a simple analogy: Imagine you're carrying a bucket of sand and you start running. As you run faster, you can carry more sand. But if you slow down or stop, the sand falls out of the bucket. The sandbar is like the pile of sand that falls out when the current slows down.