this can be used to improve the texture of the soil and provide nutrients to help plants grow.
Compost is good for all soils. It makes heavy soil easier to work and helps lighter soil retain moisture, it feeds the plants too. Use the compost in the spring or the summer. Spread it on the surface or dig it into the top 150-200mm of your soil.

mulch is material such as compost or woodchips that is used on the soil surface to discourage weed growth and keep the soil moist
To use your compost as a mulch, add a layer (about 25mm) to the soil surface leaving a gap around any soft-stemmed plants.