Client-server applications
A website works through the interaction between two computers: the client and the server. If you enter the URL www.github.com/pbugnion/s4ds/graphs in a web browser, your browser queries one of the GitHub servers. The server will look though its database for information concerning the repository that you are interested in. It will serve this information as HTML, CSS, and JavaScript to your computer. Your browser is then responsible for interpreting this response in the correct way.
If you look at the URL in question, you will notice that there are several graphs on that page. Unplug your internet connection and you can still interact with the graphs. All the information necessary for interacting with the graphs was transferred, as JavaScript, when you loaded that webpage. When you play with the graphs, the CPU cycles necessary to make those changes happen are spent on your computer, not a GitHub server. The code is executed client-side. Conversely, when you request...
