The annulus or ring is a band or bands of tissue usually dervided from the partial or inner veil that girdles the stem either near the cap (superior) centrally, or near the base (inferior)
The gills of this fungus are attached directly to the stipe but there appears to be a notch taken out of the top of each one when it meets the stipe.
Outer layer of usually thin tissue that protects the developing fruit body of some mushroom like fungi. The veil can extend from the cap edge to the top of the stem (partial) or envelop the entire fruiting body (universal).
Appendiculate is a term used to desribe the tissue overhanging the edge of the cap.
Crenate is a term which means scalloped, and is usally used in describing giils or cap margins which are regularly wavey.
Fungi are the fruiting body of the fungal organism - most of it is in the form of spidery threads that grow through the substrate, in this case the bark of a living tree.