This is a good question and it took me awhile to figure out the difference (and I might be wrong, so other ppl can reblog w/ their own explanation). 

The confusion is bc “Verse” is an abbreviation for “universe,” and “AU” is an abbreviation for “Alternate Universe.” The difference is mainly in that the former is usually applied to RP and the latter is usually applied to fanfic and fanart, but both words can be used for both. 

A “Verse” (lots of different words for this, different RPers make them up) is more for RPers, bc it’s a time period set in canon, or a non-canon time period chosen between the RPers who are roleplaying together.

– So you can have a Louis RPer and a Lestat RPer referring to “Verse:One Happy Family” (or whatever name they choose for it), which refers to the time period in canon in which those muses were living with Claudia and all three of them were happy, before Claudia started to actually grow up.

– Or, you can have a Verse that is NOT in canon, like “Verse:Italian Tales” (or whatever name they choose for it) in which a Gabrielle RPer and an OC RPer are roleplaying stories from Gabrielle’s childhood in Italy, which was not explicitly written about in canon.

An "Alternate Universe” is more typically used in fanfic or fanart in which the characters and canon have been rearranged somehow, like a female!Lestat, or the idea like: Enkil awoke in 1984 and he is mindlessly on the warpath, terrorizing the world, and Akasha is trying to enlist the other vampires to help stop him. My fave AUs are ones in which lots of canon, fanon, or headcanon is part of the story.

– There is an incomplete fanfic on AO3 called The Grim Brothers that basically casts the VC characters into a Grim’s fairy tale, and they are not vampires in it, but some things from canon are retained or reworked: Louis and David are stepbrothers, which is technically sort of true!