Web applications came from the mix of an application and a browser, of course! Basically, a web application is a client application that runs on a web browser. Thus most of the processes are done on the client machine and the server is just responsible for the data processing.
This is interesting, since you can always deliver to the client the most updated version of the application, while the client does not need to upgrade the software. This leads to fast-paced and continuous development of the app.
Just as we always say when starting a new example, let's use the HTML boilerplate that we always use, keeping the same folder structure and so on:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Web App</title>
<link rel="stylesheet...
