Usually, categories here are meant to refer to what is usually known as 'kintype'/'theriotype'/'phenotype'/'species', etc., but can refer to generic groups and movements such as 'therianthropy' and 'otherkin'. For areas such as Real Vampirism, they refer to variants in experience, or how they relate to that experience (as is with the case of vampire donors.)
These categories and their heirachies/relationships are a general guide to helpfully sort information. While many aspects of these are based on research and the ways that terminologies have been used in various circles, they are not by any means meant to be some kind of chart or factual point of reference and should not be treated as such.
While some media items discuss social and community interactions, group categories (such as 'therianthropy') are used here in a purely categorical sense; they are not intended to imply them in any identity or community sense.