How is salt naturally made into fresh water?

Answer 1

Decalination removes salt and other solutes, leaving fresh water.

An energy-intensive way is to boil the water, and condense the steam.

Possibly cheaper is to use materials such as semipermeable membranes to filter out the solutes, such as salt in salt water or brackish water. This is the process of osmosis. However, the membranes may not function indefinitely without replacement.

Answer 2

It doesn't.

If you're asking how salt water turns fresh, then here's how:

1. Salt water evaporates leaving the actual salt behind.

2. Rain brings fresh water down.