In general, it is the act of performing an action for someone else. In computing, this translates as approaching a resource (like the internet) through a different (proxy) server. This server can act as a simple gateway, but it can also add functionality to the requests it receives and sends. The most well-known proxies are the ones that allow access to resources that are restricted. For example, sites that are only open to visitors from a certain country, or the opposite, sites that are not a allowed at a certain location (work, school).