Extensions are basically libraries (.dll files on Windows and .lib files on MacOS) that Gig Performer can load and provide the additional support for a hardware device. Extensions provides your hardware device with the closer integration with Gig Performer features communicating directly with it and not with e.g. by MIDI or OSC messages.
For example, if you had a keyboard with a display and the keyboard's manufacturer created an extension for Gig Performer (with our SDK), Gig Performer would be able to communicate directly with your keyboard, and show various parameters, such as Song name, Rackspace name or Tempo on the display (or assign buttons and knobs with functions in Gig Performer).
Additionally, extensions may also provide panels and menu items that may help to use them better.
If you are a manufacturer and want to create extensions to allow Gig Performer to support your hardware devices, feel free to contact us about our software development kit.