This is an installer and updater for Wiremod for Garry's Mod. It will always download the absolute latest version, and comes with a readme to make it extremely easy to run. Wiremod is quite important if you're thinking of playing on multiplayer servers.
I am uploading it here, however, because you can view their threads and everything without making an account, but for some reason you need one to download something. Do not worry, this will not affect the updater if you don't have an account. If you're into building neat things in Garry's Mod, though, you may want to get an account over there anyways, it's pretty cool.
Oh, and, uh... the preview image is that because I've got nothing else and it requires one.