Description

1. MongoDB: MongoDB is a NoSQL database that stores data in a flexible, JSON-like format called BSON. It is commonly used in MERN applications for its scalability, flexibility, and ease of use, especially for handling large volumes of data and complex queries.

2. Express.js: Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for building web and mobile applications. It is used as the backend framework in MERN applications to handle HTTP requests, routing, middleware, and other server-side functionalities.

3. React.js: React.js is a JavaScript library developed by Facebook for building user interfaces. It allows developers to create reusable UI components and efficiently manage the state of the application. React.js is used as the frontend framework in MERN applications to build interactive and dynamic user interfaces.

4. Node.js: Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows developers to run JavaScript code outside of a web browser, making it ideal for building server-side applications. Node.js is used as the runtime environment in MERN applications to execute JavaScript code on the server side, handle incoming requests, and interact with the database.