It's also known as man-in-the-middle proxy.
The forward proxy sits on a local network between the local client (user) and the external destination website.
Technically, in order to get content from the origin server, the client sends a request to the forward proxy naming the origin server as the target. The proxy then requests the content from the origin server and returns it to the client.
A typical usage of a forward proxy is to intercept HTTP traffic and:
- to implement a web cache to reduce network usage.
- to analyze HTTP traffic (Network - Trace (Capture|Sniffer|Analyzer) Tool (Packet Analysis))
- to modify the HTTP page
The proxy can be implemented:
The client must be specially configured to use the forward proxy to access other sites. Ie the proxy parameters.
Example with Windows:
The configuration of a forward proxy on a Linux server happens with the environment variable http_proxy or https_proxy that set the proxy server location.