Flask is a micro web framework written in Python. It is classified as a microframework because it does not require particular tools or libraries. It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions.

Flask is a lightweight Python web framework that provides useful tools and features for creating web applications in the Python programming language. It is designed to make getting started quick and easy, with the ability to scale up to complex applications.

One of the key features of Flask is its simplicity. The framework is easy to set up and get started with, and it doesn't require any particular tools or libraries. This makes it an ideal choice for developers who want to get a web application up and running quickly.

Another key feature of Flask is its extensibility. The framework is built in such a way that it can be easily extended with additional functionality. This is done through the use of extensions, which are Python packages that add specific functionality to Flask. For example, there are extensions available for adding support for databases, handling user authentication, and working with templates.

In addition to its simplicity and extensibility, Flask is also known for its flexibility. It can be used to build a wide range of web applications, from small personal projects to large, complex applications. It is also a popular choice for building RESTful APIs, which are used to provide access to data and functionality over the internet.

Overall, Flask is a powerful and easy-to-use Python web framework that is well-suited for a wide range of web development projects. Whether you are a beginner looking to get started with web development or an experienced developer looking for a lightweight framework, Flask is a great choice.