The octave buttons are used to shift the keyboard up or down in one octave increments. This extends the range of the keyboard in either direction, which lets you play notes that lie outside the number of keys available.
The button is used to select independent banks of continuous controllers. Effectively, this allows you to control more independent parameters with the knobs, faders and buttons. The bank selector button is used to switch among the available banks.
The arpeggiator is the main tool used by computer musicians to generate looped material. An arpeggiator is simply a generator of signals that controls the tempo, pitch, velocity, gate, and other parameters of the sound.
The more buttons the device has, the more complex the input can be.
Navigation buttons allows users to navigate through their files/data.
The transport controls are used to control playback, set the position of the playhead, start recording, activate the cycle region, or to move to the project start or end.