As a software engineer, one of the first frustrating phrases you will hear is, "Well, it works on my machine!" This happens when code runs perfectly on your computer but fails on a colleague's laptop or a production server. The reason is usually a small difference in the environment, like a different Node.js version or a missing system library. This is where Docker comes in. Think of Docker as a way to create a standard, universal box for your application. This box contains everything your code needs to run: the code itself, libraries, tools, and settings. You build this box once, and then you can ship it and run it anywhere, and it will always work the same way. In this guide, we will take a simple Node.js web server and package it into one of these universal boxes using Docker. What You Will Need Before we start, make sure you have these two things installed on your computer: Node.js: To run our simple application locally first. Docker Desktop: The application that lets you build and run Docker containers.…