Hi JulietDelta and welcome to the forum.
MMM45 has explained the main ones I suspect you might have had trouble with. RC stands for Recruit Course, and AEAF stands for
Allied Expeditionary Air Force. All the other seem to relate to his employment in the RAF Police. Provost is just another term for service police. The event dated 22/7/44 is his disembarkation, ie
return from continental Europe - see posting below from rafcommands. Please let us know if there are any other abbreviations you don't understand.
I suspect the reasons for the redactions is that they refer to medical events. The entry towards the bottom dealing with his discharge includes a reference to KRs which are Kings Regulations. The only reason why part of the KRs, which were the authority for his discharge, would be obscured is because it referred to his medical condition.
Since you are a close blood relative you can ask for an unexpurgated copy of his record if you wish.