Proxy is a server that is positioned between computer of a client and web-resource and provides network services to client. Proxy-server redirects all queries made by client and gives response from its own cache or redirects requests to real server.
Why is the proxy-server needed? First of all it is used as a caching solution and it may enhance web response speed dramatically. When a client makes a request, caching proxy returns the answer right from its cache if the document exists. If there is no such document in cache, the query is made to real server and proxy returns result to end user caching needed file for further use.
Proxy-servers may also be used for web-content filtration. In organizations proxies are often used to block web-content from being viewed by user. Providers may use proxy to block computer viruses and other unwanted or malicious content. Companies also use proxy to block user access to certain websites, such as, for example, social media networks.