When a liquid is heated at atmospheric pressure, it typically boils at its known boiling point. This situation changes when pressure is manipulated. When the pressure is increased during the heating process, the boiling point also increases. You can read more on this at www.rifledair.com/refrigerant-behavior.
Putting higher pressure in the refrigerant system means the refrigerant has a higher heat capacity, so can absorb more heat before boiling or being circulated to the part of the system where it then releases heat.