At the core of many web apps is a REST (or RESTful) application. REST is an abbreviation of REpresentational State Transfer, which is a design pattern that deals with the fact that most web technologies are inherently stateless. Think of a standard website that doesn't require a login or much data—just static HTML and CSS, as we created in the previous chapters, but even simpler: without JavaScript. If we think of a site like this in terms of state, we can see that a bunch of HTML doesn't know our user journey, doesn't know who we are, and, quite frankly, it doesn't care. Sites like these are like printed material: you interact with it by looking, reading, and turning pages. You don't change anything about it. In general, the only way you're really modifying the state of a book is with a bookmark to save your place. Honestly, that's one step more interactive than a basic blob of HTML and CSS!
To work with users and data,...
