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. Examples of applications that make use of the Flask framework are Pinterest, LinkedIn, as well as the community web page for Flask itself.
Flask is called a microframework because it keeps the core simple but extensible. It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions. However, Flask supports extensions, that can add application features as if they were implemented in Flask itself. Extensions exist for object-relational mappers, form validation, upload handling, various open authentication technologies, and more.