A proxy is a site that can provide Internet users the access to sites that are blocked by filters, or restrictions set by Internet and network administrators. With a proxy, you have a portal to a blocked or restricted site and it is possible to avoid the settings of content filter that has been set in the network. Also, a proxy allows masking of the access to the site to ensure that there is no trace of a failure in the filter activity.
In layman's terms, a proxy has the capability to unblock websites with restrictions set at the administrator level which normally happens at school or at work. With a proxy, there is a power to temporarily modify your IP address and make you anonymous when you access blocked sites. This anonymity is what makes proxies powerful and popular especially among social networkers who would never let a day pass without visiting their favorite social sites like Facebook or MySpace. They have access through the use of a Facebook proxy or a MySpace proxy. Hence, nobody can ever hinder them from getting in touch with their contacts or friends even when they are using public networks.
One common application of proxy is a caching web proxy. This allows a cache or storage of web pages and files available on remote servers. This allows local client workstations to quickly access these frequently used pages. With a caching proxy, the URL that is accessed is searched in the local cache. If it is there, the document is displayed immediately. Otherwise, it gets fetched from the server and returns it to the requesting client and saves a copy of the page in the cache.