Every device can function as one of the following; a USB HID device (keyboard or mouse), a USB MIDI device (to control a DAW or software like QLab), or a joystick/game controller.
The MIDI Controller LC and MK1 Controller both also have 5 Pin DIN output ports to send messages to MIDI devices. (They are powered via USB and can also function as a USB MIDI device at the same time.)