I agree, it is confusing. Compost that is made at home in a compost pile is often full of weed seeds as it does not heat up high enough to kill all weed seeds. This is the compost I will dig into the soil when I am planting a new plant or layer in a raised bed beneath the topsoil. Compost that you purchase from a garden center in bags or from a professional soil company has been heated up and the weed seeds are dead. You can layer this on top of small weeds in your garden and they will die from lack of sunlight. Tall weeds and noxious weeds like dandelions will not die. But weeds will always blow in from above and can root in the new compost. Rich soil full of compost is not the favorite soil for most weeds as they have learned to adapt and love lean soil where no other plants want to live - but not all weeds prefer lean soil and some weeds will thrive in compost and soil. For best weed blocking, layer newspaper between young plants in the spring and cover with wood chips or bark chips to keep down the weeds. In England they will spread compost in mid spring to feed the perennials but by the time the weeds sprout in the compost the perennials have spread their leaves and shade out most new weeds. You will still see professional gardeners with a hoe uprooting weeds in perennial gardens that have dared to sprout from a mulch of compost. To summarize, all compost is not the same. Thick and chunky compost smothers weeds better than thin compost and newspaper with wood chips on top is still a better weed block than compost. The best of both worlds is to use both compost and wood chips. Keep growing, Marianne Binetti