PHM - Partial Head Morph - a morph that works on a small part of the head, something like a nose or lip morph
PBM - Partial Body Morph - a morph that works on a small part of the body, somthing like a navel morph or a calf morph
FHM - Full Head Morph - usually a character morph that reshaped most of the head
FBM - Full Body Morph - any morph that changes most of the body, like a custom sculpt for a character
That's the standard morphs, now for the not so standard
JCM - Joint Controlled Morph, used to help the mesh "pose" better, normally works on the base shape, but can be set to only work with a specific morph.
eJCM - another corrective morph, this time for expressions.
MCM - "Morph Controlled Morph". It's a corrective morph triggered by using another morph, just like a JCM is a corrective morph triggered by joint movement.
CTRL - a Control asset, a dial that uses Formula (ERC links) to control two or more assets, which can be morphs or bones or both.
There are other variations but this post could end up as a novel if I go through them all.