Sometimes someone makes a post that you don't want other people to see, but you don't want to offend the poster or go so far as to ban them. Hiding a post removes the post from view for everyone but the poster, so they're none the wiser.
To hide a post, click Admin Controls on the post itself, then choose "Hide Post" from the list of options.
You can see a complete list of posts that have been hidden, and un-hide them, in the Admin > Oversight > Hidden Posts interface:
