This document discusses different types of proxy servers and provides information about HTTP proxy servers and the proxy server software Proxyfire. It defines a proxy server as a server that acts as an intermediary between clients and real servers. There are four main types of proxy servers: FTP, HTTP, SOCKS, and SSL. Proxyfire is a proxy server checker that can detect different proxy types like HTTP, SOCKS, and anonymous proxies and classify them. It works by examining inbound traffic rather than just outbound traffic.