@SophiaHayter it's a fairly loose concept, honestly - the only prerequisite is anthropomorphism in some way. Most pre-Judeo-Christian cultures incorporate anthropomorphism in spirituality on some level to explore human integration with the natural world. It's deep rooted.

In the modern context? Often there are lifestyle elements, many folks immerse themselves in it. Fetish exists within that. It's not exclusively a sexual experience though; for many (me included) it's a much broader vehicle for self-expression, creative and personal, which allows one to explore identity through fictional characters. Those characters being anthro animals is just aesthetic preference, although it often carries a deeper meaning, like therianism.

The biggest draw card is community; a global association, loosely aggregated, of other folks with similar interests. It definitely isn't a monolith.