All of these techniques involve layering rotting organic matter onto the soil surface. This builds soil up and is an EASY way to create fluffy soil that is nutrient rich and ideal for growing vegetables.
The mulch also suppresses weed growth and shades the soil. The shaded soil holds moisture longer and so requires less watering.
On our garden plots, we use leaves extensively. A local RV park owner has us deliver our horse trailers to her establishment. Her staff rakes the leaves and puts them in the trailers. We then spread these leaves over all of our garden plots in the fall. We mix in some animal manures to create a carbon to nitrogen mix (an ideal compost creating mixture.)
We also use the leaves to mulch around plants after the growing season begins in the spring.
Another ingredient we use liberally is coffee grounds. Most Starbucks and other local coffee shop owners are happy to set their used grounds aside for industrious gardeners. We spread the grounds on top of the soil along with the leaves and manure.
Worms love incorporating these mulch materials into the soil, especially the coffee grounds. Having worms in your soil is very beneficial. Worms break up hard soil and their excrement is a very good fertilizer. Under mulch, worms thrive and busily do their jobs of converting mulch to soil. While growing plants remove soil fertility, these creatures are restoring and building it back up. It is much easier to maintain soil fertility and tilth when soil is mulched.
I highly recommend these methods.