Flask-RESTful is an extension for Flask, a popular web framework for Python, that simplifies the process of building RESTful APIs (Application Programming Interfaces). RESTful APIs allow clients to interact with server-side resources over HTTP using standard methods like GET, POST, PUT, DELETE, etc. Flask-RESTful provides a clean and elegant way to define API endpoints and handle requests and responses.

Key features of Flask-RESTful include:

1. Resource-Oriented: It allows you to define API resources as classes, where each class represents a specific resource or endpoint. Each resource can handle HTTP methods like GET, POST, PUT, DELETE, etc.

2. Request Parsing: Flask-RESTful provides automatic request parsing, which means it can parse incoming JSON, form data, and other request types, making it easy to access data sent by clients.

3. Output Formatting: Flask-RESTful can automatically convert Python data structures into JSON responses, making it straightforward to return data to the clients in a consistent format.

4. Error Handling: It offers built-in error handling, allowing you to easily handle various HTTP errors and provide appropriate responses to clients.

5. URL Routing: Flask-RESTful handles URL routing, so you can map different resources to their corresponding URLs in a clear and concise way.

6. Authentication: While Flask-RESTful does not provide built-in authentication mechanisms, you can easily integrate it with other Flask extensions or third-party libraries for authentication and authorization purposes.

To use Flask-RESTful, you need to install it alongside Flask using pip:

Here’s a basic example of how you can create a simple Flask-RESTful API:

In this example, we define a resource class called HelloWorld, which handles the GET method. When a client makes a GET request to /hello, the API will respond with the JSON object {'message': 'Hello, World!'}.

Flask-RESTful is an excellent choice for building APIs with Flask due to its simplicity and ease of use. However, it’s essential to consider other factors like security, authentication, and database integration when building a real-world API.