Xtras are plug-in applications (alternatively known as extensions, add-ons, or components) for Macromedia products (now owned by Adobe), in particular Adobe Director. They can be user-created, or bought from third party vendors. Adobe maintains a list of third party Xtras. Many of Director's own functions are implemented as Xtras.
Xtras are supported and available on the following products:
Xtras use the Macromedia Open Architecture which was designed to allow easy creation of interchangeable components between Macromedia products.
Xtras for Win32 must have an .X32 file extension. Xtras for the Macintosh generally have an .XTR extension. The file extension *.X16 is reserved for Xtras for Win16.