What's a "redirect"?

Most games built on the Source engine (and many others) offer a feature that allows the server owner to host custom maps, models, textures, sounds and any other content on a separate website.  The server then links to a specific folder on the site and players joining the server can download custom stuff without slowing down the server itself, and usually getting better speeds to boot!

In Source based games like Team Fortress 2, a redirect feature looks like this in the host's server.cfg: 

sv_downloadurl "http://www.yoursite/tf/"