FastAPI is a modern, high-performance web framework for building APIs with Python. Known for its speed, simplicity, and powerful features, FastAPI leverages Python type hints to create APIs that are fast to develop and execute. It is built on top of Starlette for the web framework and Pydantic for data validation, making it a popular choice for building robust and scalable applications.

Key Features:
1. Automatic Documentation: FastAPI automatically generates interactive API documentation with OpenAPI and Swagger UI, streamlining development and debugging.
2. Asynchronous Support: Provides built-in support for asynchronous programming with async/await, enabling high-performance and concurrent systems.
3. Type Safety: Utilizes Python type hints for data validation and error handling, reducing bugs and improving code maintainability.
4. Dependency Injection: Simplifies integration of components like databases, authentication, or caching with a powerful dependency injection system.
5. High Performance: Comparable to frameworks like Node.js or Go, FastAPI is optimized for speed, handling high throughput with minimal latency.

Use Cases:
- Data-Driven Applications: Creating APIs for data processing and analytics.
- Microservices: Designing lightweight, modular services in distributed systems.
- Real-Time Applications: Building high-concurrency systems such as chat applications or live dashboards.

FastAPI is particularly favored for its developer-friendly approach, reducing development time while maintaining excellent performance. Its ecosystem supports various extensions and is backed by a growing community. This combination of ease of use and capability makes FastAPI a go-to choice for modern Python API development.