The “micro” means Flask aims to keep the core features simple but extensible. It is classified as a micro web framework because it does not require particular tools or libraries. It does not mean that our whole web application has to fit into a single Python module, nor does it imply that Flask is lacking some functionality. Although, it does not support database abstraction layer, form validation, or any other pre-existing third-party tools. But it supports extensions to which we can add features to our applications.