What is meant by "progressive enhancement" in web design?

Progressive enhancement is a fundamental principle in web design that emphasizes starting with a baseline of essential functionality and then adding more advanced features on top of it. By designing for basic functionality first, developers ensure that their websites or applications are accessible to users with various devices and capabilities, including those with slower internet connections or older browsers.

This approach enables all users, regardless of their technology, to access the core content and functionalities of the site. Once this foundation is established, additional enhancements, such as richer media, interactivity, or more sophisticated layouts, can be layered on for users with more capable devices and connections. This ensures that while the lowest common denominator is served, visitors enjoy an enriched experience commensurate with the capabilities of their browser and device.

This strategic layering aligns with web accessibility best practices, as it prioritizes content and usability for all, paving the way for a wider reach and a more inclusive web experience. The other options do not align with the essence of progressive enhancement—designing first for the most advanced features or focusing solely on aesthetics neglects the needs of users with lesser capabilities, while creating accessible versions before general versions doesn't encapsulate the core idea of enhancing based on capabilities.