StudioLive_Series_III_OwnersManual_V5_EN_26042019, section 10 Monitoring Controls
"In addition to the main outputs, your StudioLive mixer features a set of monitor outputs and a headphone jack, each with its own distinct signal path. While you can use these outputs to listen to the main mix, you can also assign other signals to them, such as Aux mixes, the solo bus, or the tape input. This allows easy monitoring of your choice of signals as you work, while the full mix continues to flow from the main outputs."