Progressive enhancement is a strategy for building web interfaces in a layered fashion that allows basic content and functionality for all, while providing enhanced versions to those with more advanced software or bandwidth. It involves layering interface elements from semantic markup and baseline styles through to modern styles and behavior scripts. This approach simplifies development, reduces bugs and improves performance by supporting all users regardless of browser or connection capabilities. It also helps future-proof solutions and make them more mobile-friendly. The document provides further details on key technology enablers and recommendations for implementing progressive enhancement.