Wikipedia has a good albeit basic range of definitions. For those of us who passed Euro exams, some potentially useful brain space has been taken up with this antiquated nonsense.
(But it would be nice to find a single Australian pilot who knows what QNE is.)
The Q codes themselves are not abbreviations. But it can be useful to think of them that way. Thus:
QDM - Q direction magnetic? (What magnetic bearing should I fly to get to the station?)
QDR - Q direct radial? (What radial am I on?)
QTE - Q True bEaring? (What bearing am I on, from the station?)
QUJ - no abbreviation, I'm not imaginative enough. What true bearing should I take, to reach you?
Obviously, QDM / QDR are reciprocals of each other for short-range queries. Same for the other two.
Relative bearings? Hard to teach without pictures, and preferably a model plane.