Progressive Enhancement Progressive Enhancement :
It was constructed for low version of the browser page, to ensure the most basic functions, then advanced browser for the conduct effect, interactive and other improvements and additional functionality to achieve a better user experience.
Graceful degradation Use the graceful degradation :
Start to build fully functional, and then the low version compatible for browsers.
the difference:
Graceful degradation is complex from the beginning of the status quo and trying to reduce the supply of the user experience, and progressive enhancement is from a very basic, capable of functioning version, and continue to expand to meet the future needs of the environment. Downgrade (graceful degradation) means looking back; and progressive enhancement means looking ahead, while ensuring its roots in a safe zone.