The ADF Mobile framework architecture is based on a hybrid mobile architecture and is an extension of, what is also known as, Apache Cordova. The current version of ADF Mobile does not officially support native Cordova (PhoneGap) extensions.
Apache Cordova is open source fork of PhoneGap, now acquired by Adobe, providing a set of device APIs that allow a mobile app developer to access native device function such as the camera or accelerometer.
Plugins are pieces of native code (Android, iOS, BlackBerry, etc) which implement features specific for a platform, utilizing the native device functionality. Basically, with a plugin you can code whatever a device supports - even working with bar code scanners, printers and such.
See here a demonstration how these plugins can be utilized with ADF as a bridge to the native platform your application is running on. This is however an unsupported method. Watch the video to learn how:
Note once again, that this method is not officially supported.
It could break your application and/or it could make it impossible to upgrade your application to future ADF Mobile versions.