difference between compost and topsoil
Compost: The rich black soil-like result of decomposed leaves and other plant materials. Compost is high in organic matter content and is the perfect plant food, soil amendment and disease fighter. You want 'finished compost', where few to none of the original ingredients are discernable.
Topsoil refers to the uppermost layer of the earth's surface. Depending on the location, it may be a few inches to several feet thick. The slow weathering of rocks and decay of organic matter produces topsoil over thousands of years, releasing nutrients back into the soil, where plants use them.