npm stands for Node Package Manager, which is used for managing packages, or modules, that are used in Node.js applications. Modules are like libraries in other programming languages, which contain pre-written code that can be used to perform specific tasks or implement certain features.

There are two types of modules in Node.js - core modules and third-party modules. Core modules are already built-in modules that come with the Node.js installation, while third-party modules are external modules that can be installed using npm and used in your Node.js application.

To install a third-party module, you can use the npm install command followed by the name of the module. For example, to install the popular Express module, you would run the npm install express command in your terminal.

Once the module is installed, you can use it in your application by requiring it using the require() function. For example, to use the Express module in your application, you would add const express = require('express') to the top of your file.

npm also allows you to manage dependencies, which are other modules that are required by your project. When you install a module using npm, it will automatically install all of its dependencies, which are listed in its package.json file.

Overall, npm is a powerful tool for managing modules and dependencies in Node.js applications, allowing for easier development and better code organization.