Intelligently splits oscillators based on the number of notes played. For example, playing one note uses all four oscillators, while playing two notes assigns two oscillators per note.
Video guides like the Korg MonoPoly Tutorial and Demo or Creating and Explaining Synth Sounds provide visual walkthroughs of the controls. Korg MonoPoly Tutorial and Demo
You can download the official Mono/Poly Owner's Manual or the Setting Chart from the KORG Support page.