what is a saturated?

Answer 1

In general usage 'saturated' means 'full' but it comes from chemistry and the meaning in that context means that a solution will no longer dissolve any more solid.

For example, take a glass of water. If you add salt, the salt will dissolve into the water. If you keep adding salt you will get to the point where it will no longer go into solution. At this point the water is saturated. Try it.