Luke
The "Q" codes date back to "HF" aka High Frequency radio transmission, aka Morse Code! Every tx was as short as poss [for obvious reasons]. Any "really" ancient STPO/WTO could give you a "full" translation.
From what I can remember, QNH Regional applied "Sea Level Atmospheric Pressure"
QFE Aerodrome Altitude Pressure
QGH Climb [in orbit] to cruising level above a/f
In short, [Regional] QNH means that ALL a/c "should" be on the same setting, and hopefully miss t'other one
QFE Your altimeter reads zero on the ground
"Standard" QNH 1013.2mb/29.92in is used for flying above the transition level [approx 4500ft] so that ALL a/c KNOW that they are separated by 1000ft on Airways, or even IFR in the "Bundu"
hope this helps
we aim to please, it keeps the cleaners happy