Components of the Web

The Web is made up of 3 general components.

1. Origin Servers
2. Clients
3. Proxy: (See this, which im reproducing )  There are four kinds of widgets that people might call proxies. Note that the term "widget" below may be either software, hardware, or a combination.
1. A router is a widget that sends packets back and forth between multiple network segments (i..e., between ethernet, ADSL, and LocalTalk networks all coming in to the same machine, but possibly on different ports or cards). The widget may choose to filter out some packets and not route them. Important characteristic: multiple networks attached.
2. A gateway is widget that translates data from one protocol (like TCP/IP) to another protocol (like AppleTalk) as it flies past. The widget may also choose to not translate some packets, and filter them out.Important characteristic: protocol translation.
3. A proxy is a widget that receives requests with its left hand (usually from one network), and then launches similar requests with its right hand (usually on a different network). As the results arrive back at the right hand, they are copied over to the still-waiting left hand and returned to the original client. (It acts as a server with its left hand, and as a client with its right hand.) The widget may filter out certain requests or certain responses and not copy them from hand to hand. Important characteristic: acts as both client and server. When a proxy operates at the packet level it is a transparent proxy, and the clients usually don't know that there's a proxy involved.
4. A cache is a widget that receives requests and either responds directly from it's own store of information, or forwards the requests "upstream" to another server. When data comes back from the upstream server, this widget keeps a copy of the data for itself, and also returns the data to the original client. Important characteristic: data stored locally.