A proxy is a site that allows users to visit other pages through the usage of the site itself. Basically they are just a tool that allows a user to hide they IP address in case that the page that they are trying to visit a page that is bloked for their IP for some reason. This is done mostly in schools and certain countrys so that in case of the schools students don't spend schools resources to download stuff for their personal needs, and in countrys cause of the orders of the rulling goverments. To use a site like this you just have to enter a URL of the page that you are trying to visit and press some button (in this case Go) to start visiting that URL. Enjoy.