Flask takes the flexible Python programming language and provides a simple template for web development. Once imported into Python, Flask can be used to save time building web applications. An example of an application that is powered by the Flask framework is the community web page for Flask.
Flask is called a microframework because it keeps the core simple but extensible. There is no database abstraction layer, form validation, or any other components where third-party libraries already exist to provide common functionality. However, Flask supports extensions, which can add such functionality into an application as if it was implemented in Flask itself. There are extensions for object-relational mappers, form validation, upload handling, various open authentication technologies, and more.