An emergency condition is classified in accordance with the degree of danger or hazard present:

a) Distress is a situation when safety is being threatened by grave and imminent danger and requires immediate assistance.  The spoken word for distress is MAYDAY and is pronounced 3 times. 

b) Urgency is a situation where the safety of an aircraft or other vehicle, or of some person on board or within sight is threatened, but does not require immediate assistance.  The spoken word for urgency is PAN PAN and is pronounced 3 times.

When canceling a MAYDAY or PAN you would say the following:
MAYDAY, ALL STATIONS, ALL STATIONS, ALL STATIONS, SILENCE FINISHED, OUT.