Those are the pages that are not editable from the wiki:
Silly question, does it make sense, to have a Locked page, if it can be modified?
– Gerald Klix
Well, it works pretty well against dumb spam bots, plus you can lock the Locked page itself when it gets nasty – you just can't do it from the wiki, you have to use a text editor. – Radomir Dopieralski