Using Mulch
The term mulch is used for a variety of organic products, which decompose and can serve as decorative ground cover or as soil improvement.
Shredded bark (or bark dust) is made of common local tree bark (ie. cedar in California, Douglas fir in Oregon etc.) in varying sizes, which is used primarily as a decorative ground cover to retard weed growth.
Eventually, mulch breaks down to become part of the soil. Humus or black humus, for instance, is a decomposed wood product used primarily for soil amendment or improvement. You might find other types of mulch in your area.
-- Tips courtesy of HomeAdvisor.com