HyperText Transfer Protocol (HTTP)
HTTP is a stateless protocol. A stateless protocol means that there is no state being stored on the server, which, in turn, means that the server forgets everything once it has sent a response to the client. Consider the following situation:
You've typed http://example.com
in your browser. When your request hits the server, the server is aware of your IP address, your requested page, and any other headers associated with your HTTP request. It fetches the content from the filesystem or database, sends the response to you, and then forgets about it.
Upon every new HTTP request, the client and server interact as if they're meeting for the first time. So, doesn't that mean our earlier Facebook example is true in the real world as well?
Essentially, that is the case. All websites use cookies for authentication purposes, which is a way to fake the statefulness of a protocol. Remove cookies from every request and you will be able to see the raw, stateless HTTP protocol...