Quote:
Jetpack is Mozilla's new API for developers to create add-ons for the Firefox Web browser. Currently, many Firefox add-ons work through an extension called "Greasemonkey," which some fear may disappear if Jetpack takes off. Jetpack, however, has its advantages in terms of compatibility and the ability to activate new features without a browser restart.


More Info...
http://www.linuxinsider.com/rsstory/67139.html