Modules are just small programs you can integrate with the bigger program you are writing.
Modules would be listed in your package.json.
There are 3 types of modules.
'Core' Node modules come with Node automatically.
Examples of common core modules are http, fs and path.
There is a list of all the core modules and their methods on the Node.js website.
There are thousands of open-source, 3rd-party Node modules that other clever people have written. You can download useful 3rd-party modules (also known as "packages") from npm (the node package manager).
The npm website says:
npm makes it easy for JavaScript developers to share and reuse code, and it makes it easy to update the code that you're sharing.
The npm command-line tool comes automatically with Node. You can install 3rd-party packages on the command line, so no need to download from the npm website or anything.
Also called a module, but slightly different from the first two.
These are modules you write yourself in your code. We will talk about this later on in step 7.