Flask is a lightweight, open-source web framework for Python, designed to help developers build web applications quickly and with minimal code. It is highly extensible, with a simple core that can be easily enhanced using various extensions for database integration, authentication, and more.

Features of Flask:

• Extensive support for extensions to add features like database integration, form handling, and user authentication.
• Secure cookies for managing sessions and user authentication.
• URL routing for easy mapping of URL patterns to views or handlers.
• Comprehensive documentation and a large community for support and resources.

Run these commands:
$ open http://localhost:5000

Disclaimer: Flask is open-source software provided under the BSD License. It is offered "as is," without any warranty, express or implied. Users are responsible for ensuring the ethical and legal use of Flask in their projects.