Flask is a lightweight, micro web framework in Python designed for building web applications with minimal setup. It provides essential features such as URL routing, request handling, and template rendering while allowing developers to integrate additional components as needed. Unlike Django, which follows a "batteries-included" approach by providing built-in functionalities like an ORM, authentication system, and admin panel, Flask takes a more modular and flexible approach, giving developers greater control over their stack. Flask is ideal for small to medium-sized projects, microservices, and APIs, whereas Django is better suited for large-scale applications that require rapid development with built-in security and scalability. Flask’s simplicity makes it easier to learn and customize, while Django enforces a structured, convention-over-configuration design, making it more robust for complex applications. Ultimately, the choice between Flask and Django depends on the project's size, complexity, and the level of customization required.