Welcome! Let's embark on a journey into server-side programming, starting with Node.js.

Before we pound the pavement, let's briefly define two core terms of web communication: server and client. You can think of the server as a chef - it prepares (serves) data or information. The client, on the other hand, is like a restaurant guest - it requests and receives this information and renders it on the web page. Together, they carry out web interactions.

Now, back to Node.js. So, what exactly is Node.js? It's a JavaScript runtime built on Chrome's V8 JavaScript engine, which allows you to run JavaScript on your computer. In other words, it enables you to use JavaScript outside of a browser! With Node.js, you can interact with your computer's file system much as you would with other server-side languages such as PHP or Python.

Next, let's explore Express.js. It's a flexible Node.js web application framework that offers a robust set of features for web and mobile applications. Although the name might sound intimidating, rest assured that it's a user-friendly library.

Express.js enables us to manage everything, from API routes to requests and views. It's incredibly adaptable and pluggable, providing everything we need straight out of the box.

To use Express.js in your application, just require the "express" module in a Node.js file as shown below:

With Node.js and Express.js at the ready, let's proceed and create a simple server. Here's a piece of code that constructs a server that responds with "Hello World!" to all requests: