A spikelet of wheat is an inflorescence with 1~ several florets inside, and a pair of glumes outside to wrap all the florets (equivalent to the involucre of an inflorescence). The outer layer of each small flower has a lemma and a palea, and the lemma is slightly larger and wraps the palea. Further inward are the two leaves at the base, followed by stamens and pistils.
As for the prickly thing upstairs, it is an extension of lemma and is called mans.