Kohana is a lightweight, open-source PHP web framework that follows the Model-View-Controller (MVC) architectural pattern. It aims to be secure, fast, and easy to use, with a focus on minimalism and extensibility. Kohana provides a robust set of tools and libraries for building web applications, including database abstraction, input validation, caching, and authentication. It also has a flexible routing system that allows developers to easily create clean and SEO-friendly URLs. Kohana is known for its simple and elegant code, making it an excellent choice for developers who want to create scalable and maintainable web applications.