Keen aficionados of any phenomenon such as authors, ideologies or fashions (fans
) can collectively manifest as fandom
typically are interested in even minor details of the object of their fandom; this is what differentiates them from those with only casual interest. The objects of fandom are typically artistic, sporting or entertainment related. For example, it would not be usual to refer to an accountant who is really interested in the details of accounting to be a "fan" of accounting.
A derogatory term for a member of fandom is "fanboy".
See in particular Science fiction fandom, Furry fandom