Mulch is a covering placed around plants (or covering the ground in lieu of plants), mainly to prevent the growth of weeds.
But, whether placed around plants or spread out over bare soil, a garden mulch provides advantages that go beyond weed control, as will be laid out below.
Most of these materials will break down over time, helping with soil nutrition. When they break down, they add organic matter and nutrients to the soil
For This Reason
one can say that they eventually serve as soil amendments. They are sometimes called "organic" mulches.
Be careful, though, in choosing to use stone as a mulch. Make sure that you really want it to be covering the ground in the area that you have chosen for it. This is because, once in place, stone is very hard to get rid of.
If you change your mind about having it there later and try to remove it, you will find yourself having to fish a bunch of small stones out of the soil. And remember, stone does not break down into the soil, the way a bark mulch does.