Complex sentence: The boundary criteria between IMC and VMC are known as the VMC minima and are defined by: visibility, cloud ceilings (for takeoffs and landings), and cloud clearances.
Split into simpler sentences: The boundary criteria between IMC and VMC are known as the VMC minima. Visual meteorological conditions are usually defined by certain visibility minima, cloud ceilings (for takeoffs and landings), and cloud clearances.