Rascal ...
My working definition of mulch is any plant organic material you put down to both deter weeds and to maintain moisture in the top of the soil.
I have used shredded leaves, pine needles, straw, partially decayed wood chips and more.
Do take the time to learn about mulch. It's one of the very best ways to improve your soil and to help your garden. As the mulch decomposes, it feeds the soil. Also, keeping the soil moist helps create the environment for worms and other beneficial soil bacteria. It's a win all the way around.
I don't buy mulch because I live in the midst of a forest and can go out and collect my mulch materials.
If you click on the button to the left on the navigation bar ACCESS THE IDEAS POSTING AREA and enter "mulch" in the search field, articles and ideas about mulch submitted by ATP members to the site will come up and provide you with a lot of reading.
Then, if you feel like you have more questions about mulch, just use the ASK A QUESTION forum.