Shrines are little mini websites dedicated to specific topics that the webmaster is really passionate about, typically found on the old web and places like Neocities that try to recapture that spirit. I believe the term originated within the context of fan websites, but I've seen it extended to more general things besides fandom/character shrines. I don't actually fully know where the term originated and it's very difficult to look up... you tend to run into religious websites or real life shrines!
Currently I have one shrine developed enough for a bit of exploration:
As well as one shrine that is still very much under construction (because I am very lazy lol):