Resref is short for Resource Reference. Each creature, area, item, and anything else you can think of has an associated resref or file name. These are useful to know for editing purposes and for using the debug window. Below are lists of resrefs.
Areas-This list of area resrefs is far from complete. I will try to update it eventually.
Spells-This is the spell list that I exported from ShadowKeeper. The list follows this format-
Spell Type,Spell Level,Spell Name, ResRef.