The idea surrounding this is simple, the SCP Foundation is a special secret organization that goes around the world and gathers/collects/detains anything that may serve as a threat to the world or causes some sort of strange effect to the people. Anything kept in their facility could be people with strange powers, monsters or aliens, dangerous or cursed objects, and everything else in between. This website contains the reports on these things, the people involved, tests done, and other sorts of things.
SCP Foundation originated from creepypasta (scary stories about almost anything) on the 4chan boards and was then moved over onto its own website. It's a sort of fun website that us b-movie fans can enjoy and get scared at. Lots of interesting things can be found it. So feel free to check it out!
TV Tropes Page:http://tvtropes.org/pmwiki/pmwiki.php/Wiki/SCPFoundation
Most famous creation and terror:http://scp-wiki.wikidot.com/scp-173