Flask is a lightweight, open-source web framework for Python, designed to facilitate the rapid development of web applications. Known for its simplicity and flexibility, Flask follows the WSGI (Web Server Gateway Interface) standard and the minimalist "micro-framework" approach, providing only the essential components needed to build web applications. It includes a built-in development server, integrated support for unit testing, and a flexible templating system based on Jinja2. Flask's modular design allows developers to choose and integrate additional libraries and tools as needed, making it highly customizable. Its straightforward and unopinionated nature makes it an excellent choice for both beginners and experienced developers who want to create scalable and maintainable web applications quickly. By enabling rapid prototyping and providing a clear and concise API, Flask empowers developers to focus on writing code and building features, making it a popular choice for web development projects.