100% Wool vs Wool Felt
Felted wool is a woven textile that has been washed and agitated causing the fibers to shrink (known as felting). Felted wool fibers make the weave of the fabric very tight and resistant to fraying. Because it's woven, the texture is softer and drapes nicer than the felt options. So wool used in items that might need washed, you would want felted wool (washed wool.) Note: The Wool Club only sells washed wool)
Ever wonder why wool isn't pure white like snow well, wool fibers are naturally off-white, ever seen a snow white sheep? You won't find a pure white felted wool. To whiten the fibers, one would have to be bleached which causes damage. A bright white can only be found in wool felt blends.
Wool Felt is a composite material where wool fibers are pressed together to create a sheet. The matted fibers are very dense, resulting in a stable fabric for appliqué. The texture tends to have more body than felted wool, but quality wool felt brands are not at all stiff.
Wool felt blends are composite material made of wool fiber and rayon ( a man-made fiber created from wood pulp). The two are blended together and formed into a sheet. Like wool felt, the fibers are tightly blended making it a suitable material for appliqué. Wool felt blends tend to be more stiff and have a textured surface.
If you are doing a project where a dimensional element you will want to choose a wool felt or wool felt blend since the stiffness of the material will add structure.
One other felt that we should mention is craft felt. This is the inexpensive felt you see in craft stores (usually near the kids crafting section). It is made from 100% synthetic fibers. Colors are usually very limited. While it is good for some crafts, I don't recommend it for stitching projects.