Do you have bare dirt?
Soil doesn't much like being naked. Soil, like most living things, enjoys some level of protection from the elements. Mulch is like clothes for soil. It protects from heat, cold, drying out and weeds. Mulching means less work for you (which I love!) because bare soil is labor intensive -- it requires too much weeding, watering and other maintenance.
You can spend a lot of money on designer mulch at a garden center, or you can make your own mulch from organic material like fallen leaves and lawn clippings that you gather up in your yard.
When you collect leaves in the fall (run over them with your lawn mower to crunch them up) then rake them into piles protecting the bases of your shrubs, trees and perennials, you are mulching. Mulch is organic material collected to form protective layers on top of exposed areas in your garden. Instead of throwing away all the organic matter your lawn and trees invest in their leaves and blades, why not recycle them back into your yard? Mulch is like hand-me-downs: sweaters, pants and fancy dress-wear going from big sister who has outgrown their usefulness to little sister who needs something to wear.
Hand-me downs you can eat!
As the mulch breaks down, it adds nutrients to your soil. Hand-me-downs you can eat when you're done wearing them? What's not to love?
Enough mulch placed on top of plants will kill them. Smothering weeds with mulch is an effective method of weed control.
Mulch placed around plants will protect them from weeds, drought, heat and cold. There isn't a drawback to mulching.
Types of Mulch:
Organic vs. inorganic mulch: inorganic mulch refers to sheets of plastic or other man-made materials used to keep weeds down and protect soil. Inorganic mulch is practical in large-scale farm gardens where productivity is important and looks are not. Inorganic mulch can be a valuable tool for the organic gardener who wants to control weeds without adding chemicals to the soil.
Organic mulch is made from plant materials: straw, lawn-clippings, wood chips, compost, shredded bark, sawdust and dried leaves are excellent organic mulches.
Decorative mulch: mulch is like clothing, it can be extremely plain or haute couture. Hazelnut shells, crushed seashells, stones, gravel, natural or died wood chips, cedar and other hardwood bark of every size, even rubber pellets and glow-in-the dark sand can all spiff up your yard for a fancy occasion.
Your budget, tastes and imagination dictate which mulch works best for you.