Using mulch is a good gardening habit but not mandatory; the benefits, however, make it worth the effort. A really good job of mulching your garden usually offers these benefits:
In cold-winter areas, protects plant roots from winter cold and helps prevent frost-heaving, in which plants are literally pushed out of the ground by the natural expansion and contraction of the soil as it cools off and heats up
The “right” or “best” mulch to use depends on your climate, the part of the country you’re in, and the part of the yard you’re using it in. Some mulches are free, while you can purchase others locally. Experiment to find out what you and your plants prefer.