In mosses plant calyptra is a cup shaped structure which is formed from the archegonium. The calyptra is attached to the capsule which will protect the sporophyte and it will fall off after the capsule matures.
Whereas the operculum is an apical portion of the moss capsule which is also a cup shaped structure. The operculum is also known as the lid of the capsule and is the terminal end of the capsule.
