Max Continuous power refers to the engine power that's allowed to be used continously in a de-rated engine , as opposed to take-off power which usually has a 5 minute limit.
For example,
The R22 engine is de-rated from 160 HP to 124 Hp (75% max rated power) for Max continuous use on a standard day.
The R22 Max takeoff power of 131 HP is about 80% MRP. (Monitor the cylinder head temp gauge on take off at low DAs)