A web proxy server acts as an intermediary and gets the web content for you bypassing web filters and sending the web site directly to your browser. Most web proxies are free, anonymous, and also helpful for protecting your online identity while browsing the world wide web.
Many employers use web filters so that its staff cannot access social sites like FaceBook and free Web mail services such as Gmail etc. Schools, universities and certain countries also block access to what they see as inappropriate, dangerous web sites including political criticism.