Mulches are gardener-applied ground covers.
The term mulch refers to a ground cover artificially applied to mimic natural leaf cover. Mulches are usually applied to provide nutrients, retain moisture, reduce erosion, for visual appearance, and/or suppress weed growth.
A range of different materials can be used for mulching, including wood chips, pine needles, leaves, cardboard, manure, compost, grass clippings, and gravel. Note that most of these are organic in origin and will eventually break down. Some will provide nutrients (e.g. compost) whilst others will change the soil chemistry and deter the growth of particular plants (e.g. pine needles).
Use these tags for all questions about applying mulches. Questions about specific mediums (e.g. "how to create compost") should use the appropriate tag instead. Use the mulch tag for questions about applying these mediums.