A RESTful API is an architectural style for an application programming interface (API) that uses HTTP requests to access and manipulate data.

REST APIs are widely adopted because they:

• Separate frontend and backend - Enables independent development and deployment of client and server applications, avoiding monolithic architectures where everything is tightly coupled
• Enable multiple clients - A single API can serve web applications, mobile apps, and third-party integrations simultaneously
• Improve scalability - Backend services can be scaled independently based on demand without affecting the client applications
• Facilitate team collaboration - Frontend and backend teams can work in parallel using agreed-upon API contracts
• Promote reusability - Business logic and data access are centralized and can be reused across different applications

Node.js allows JavaScript to run on the server side, making it possible to use the same language for both frontend and backend development. It's particularly well-suited for building REST APIs because of its non-blocking, asynchronous architecture that efficiently handles multiple simultaneous requests, and its vast ecosystem of packages (npm) that speed up development.

Express is a lightweight web framework for Node.js that simplifies building REST APIs. It provides an easy way to define routes (URL endpoints), handle different HTTP methods (GET, POST, PUT, DELETE), and process requests and responses with minimal code.

MySQL is a popular open-source relational database management system (RDBMS) that uses Structured Query Language (SQL) to manage and organize data. In a REST API, MySQL serves as the persistent data storage layer where application data is stored in tables with defined relationships.

MySQL is well-suited for REST APIs because it:

• Provides reliable data storage with ACID (Atomicity, Consistency, Isolation, Durability) properties
• Supports complex queries and relationships between data tables
• Scales well for applications of various sizes
• Integrates easily with Node.js through libraries like mysql2