What's the difference among/between...

[pgym]

In VERY broad terms:

arrangement - reconceptualizing a work via reharmonization, melodic paraphrasing, orchestration, or development of the formal structure

transcription – a) copying and/or rescoring of music; or b) a notation of a previously unnotated work

orchestration - the assigning of notes to instruments, either in the course of composition or adaptation

(musical) setting - a musical composition written or arranged to fit a literary text