Imageboards can be largely divided into two categories: those derived from Futaba Channel, i.e. linear imageboards; and those derived from Danbooru, i.e. nonlinear imageboards. Danbooru is named after the Japanese word for "corrugated cardboard", and from Danbooru's name comes the suffix -booru to denote any similar nonlinear imageboard, much like how -chan has become a suffix for linear imageboards, after Futaba Channel (i.e. 2chan).

Danbooru is centered on anime, manga, and otaku culture more broadly, and does host plenty of perfectly innocuous fan-art, hence why the site might appear in image search results on Google or DuckDuckGo or whatever... However I think it's safe to assume that a majority if not vast majority of Danbooru's traffic comes from people wanting to look at all the porn hosted on the website: the site's non-linear nature — i.e. its system of elaborate tag-based searches — makes it perfect for people with very niche hentai fetishes to find, as it were, zurineta... Including, despite Danbooru not (yet) being banned in Norway, zurineta of a type which is effectively banned in Norway under court and police interpretations of Straffeloven § 311 (a law which is phrased so poorly that Sauls Goodmen try to argue that so-called "lolicon" is Actually Totally Legal Here), as well as zurineta of a type which the Storting inexplicably decided not to ban earlier this month.

But yeah, all in all, if you ever come across a Danbooru link while surfing the Web, then you should probably let that link stay blue — unless you know and are willing to accept any risks involved with clicking the link, from the legal issues to the experiencing your own personal Agony in the Garden. I know there's something called Safebooru which is supposed to be a mirror of Danbooru without all the porn, but I can't speak for where exactly Safebooru draws the line between SFW and NSFW, so I don't know if I can recommend it. I myself have not really used imageboards of any kind since I was a teenager browsing Derpibooru.