What is expressJS? Answer : Express is a relatively small framework that sits on top of Node.js’s web server functionality to simplify its APIs and add helpful new features. It makes it easier to organize your application’s functionality with middleware and routing; it adds helpful utilities to Node.js’s HTTP objects; it facilitates the rendering of dynamic HTML views; it defines an easily implemented extensibility standard. This book explores those features in a lot more depth, so all of that lingo will be demystified soon. What Express is used for ? Answer : In theory, Express could be used to build any web application. It can process incoming requests and respond to them, so it can do things that you can do in most of the other frameworks mentioned earlier. Express is often used to power single-page applications (SPAs). SPAs are very JavaScript-heavy on the front end, and they usually require a server component. The server is usually required to simply serve the HTML, CSS, and Java