Proxy Classes

A transparent proxy is a proxy that does not modify the request or response beyond what is required for proxy authentication and identification.
A non-transparent proxy is a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation services, media type transformation, protocol reduction, or anonymity filtering."

Anonymous Proxy server does not send HTTP_X_FORWARDED_FOR variable to host, this improves privacy since your IP address cannot be logged. Anonymous proxy does not transfer the information about the IP-address of its user, and thus effectively hide the information about you and your surfing interests. In addition, some proxies (the so-called elite proxies) can also hide the fact that a user surfing through a proxy server. So there are two types of anonymous proxies (see below).

Elite proxy (high anonymity) does not send HTTP_X_FORWARDED_FOR, HTTP_VIA and HTTP_PROXY_CONNECTION variables. Host doesn't even know you are using proxy server and of course it doesn't know your IP address.