A monitor represents the configuration of the monitoring of a specific module or component within a system (ie: Users, CPU, Response times, etc…)
One monitor can usually only be assigned to one type of connector (ie ABAP buffers monitor can only work with ABAP connector)
Via a set of filters, thresholds, severity, periods and other specific parameters, you can configure in details how a monitor will perform and what kind of data it will produce (alarms, metrics, etc…)
You can for instance configure a large scope monitor picking any event on any instance as well as reacting to a specific event, for a specific user on a specific instance.
The actua monitoring is defined in the monitors
The same monitor can be configured differently across different profiles