Mulch is any material that is placed on top of the soil in a garden. There are many people that use it as nothing more than a decoration that’s meant to do little more than draw the eye for a few seconds, which is a shame since it has many uses and is very beneficial to almost every garden you can find it in. Not only that, but the very process of mulching is very useful all by itself.
Source: http://www.infotype.com.au/mulch-giving-old-trees-new-role-garden/