Definition - What does Moonlight mean?
Moonlight is an open-source version of Microsoft's Silverlight browser plug-in that runs Silverlight applications on Linux and Unix operating systems. It features a robust runtime Web application environment, enhances video/animation and supports desktop applications.
Moonlight is the only open-source project that provides easy Silverlight access for Linux users. Many popular Linux distributions have integrated Moonlight into Web browsers, such as Mozilla Firefox and Google Chrome.
Techopedia explains Moonlight
Moonlight is compatible with any 32-bit or 64-bit Linux distribution for Firefox or Chrome and supports 1.0 and 2.0 engines. Moonlight's first version - Moonlight 1.0 supports Silverlight 1.0. Moonlight 2.0 supports Silverlight 2.0 implementation.
Moonlight 1.0 has a pure C++ engine under the terms of the GNU Lesser General Public License (LGPL). Moonlight 2.0 has a graphical C++ engine. Moonlight implements a proprietary pipeline and uses the ffmpeg codec to decode audio and video. A separate profile may be used for debugging.
Moonlight has certain external dependencies, like XULRunner, Gtk+ 2.0 and ffmpeg. Moonlight 2.0 provides better multimedia streaming than 1.0.
Moonlight applications extend beyond Web browsers via desktop widgets known as desklets. Moonlight codecs are provided by libavcodec, which is part of the Debian archive or Microsoft's binary codec package. This codec pack is automatically provided if a video cannot be handled by ffmpeg.
Windows Media packages are not available with Moonlight plug-ins - they must be downloaded from Microsoft upon detection of Silverlight media content. Third-party Moonlight distributors may play only unpatented media, which supports other licensed formats negotiated by distributors and media codec owners.
Moonlight cannot play encrypted content because it is not equipped with the portable Microsoft PlayReady Digital Rights Management (DRM) software.