Now that we understand what a dynamic webpage is, we are ready to understand the meta-page: the website; the app.
The exception proving the rule, we make ourselves a batch of cookies to give us stamina; keeping it straight and simple.
We formally call the gui, the client. Assuming nothing more fancy than a username and password with which to identify ourselves, the client, we find that it is inconvenient and insecure for this to be transmitted with each interaction--each request.
We therefore allow the server to send us an arbitrary string, which we associate with that server alone. By sending it back to the server, it may now identify us (a session cookie). This is the aim.
I would like to add features to my site which would allow people to, for instance, choose the size of the text.
I would not need to identify the visitors to my site for such a feature as the identifier I send to them will merely contain their preferences.
Doing so, however, I would put myself at fault in terms of laws which exist in other places; and I do not want to exclude those visitors.
And just try to catch me following nincompoop laws of silly places!