Flask and Django are both popular web frameworks used for developing Python-based applications. While Flask is known for its flexibility and lightweight design, Django is known for its comprehensive features and powerful tools. Flask is ideal for small to medium-sized projects, whereas Django is better suited for larger, more complex applications. Flask is easy to set up and learn, but may require more customizations, whereas Django has a steeper learning curve but comes with built-in features like an ORM, admin interface, and authentication system. Ultimately, the choice between Flask and Django depends on the specific needs of the project and the developer's preferences.