APM agent(An agent that resides on a monitored system and gathers exception and performance information from a monitored application and reports it to the APM service)
Application Performance Monitoring agent(An agent that resides on a monitored system and gathers exception and performance information from a monitored application and reports it to the APM service)
monitoring pack(A kind of management pack that contains the definition of the model against which an application will be monitored and the logic to monitor the health and availability of that application)