>>2652054I can answer for sankaku which I know better than gelbooru even though they work in a similar way.
there are different types of tags
red=artist
purple= copyright (for example in this image) idolmaster_cinderella_girls
green= character names
light blue= appearance and description of the image ( i meaning the quality of the image or the type)
orange image description ranging from how many characters are in the image to what they are doing in the image
brown tags are generic tags like loli shota milf hetero etc etc etc
purple again is also used for third-party tags like deepcreampy or third-party-edit
example image
https://chan.sankakucomplex.com/it/post/show/21764118Note 1: if you don't see it, it's because you don't have an account.
note 2 shocked content (like gore) and blocked artists are reserved for those who pay, so if you are a fan of that crap, this is not the site for you.