it forces your browsers to drop all cached files stored locally and get newer versions from the site you are viewing. Your browser stores files instead of reloading them from the web all the time to make repeat viewing quicker. This can cause a problem where the site has been updated in some way, as you will still be using old versions of files. It's like a super refresh
How could the cure for world hunger be enemas? That just doesn't make any sense. edit: for one thing, somebody would have figured that out before now wow, this is cool