Commercial felting is the proccess used to create sheets of felt sold at craft and fabric stores. While these are different than the felting projects you can make at home, if you look closely at these sheets, you can see all the fibers used to form the fabric.
Needle (or punch) felting is a process originally developed for making industrial felt. Large beds of steel needles are moved in and out of the loose fiber to create large sheets of felt. The felt needle has rough, notched edges that force the fiber down causing it to entangle with other fibers and create felt.
Wet felting is what this tutorial will focus on. With wet felting, you can create a soft, dense cloth using wool. The process uses heat, agitation, and moisture to shrink and bond the fibers of the wool together. Don't let this description scare you away from trying wet felting, all you need is some yarn and a washing machine really!