Monitor service on a site server lets you perform agentless monitoring. Monitor service is installed on the Notification Server computer by default.

See About agentless monitoring.

Because monitoring can be resource-intensive, you can distribute the monitoring load to other site servers to reduce the load on Notification Server. You can also remove monitor service from the Notification Server computer to further reduce the load on this server.

See Setting up a remote monitoring site server.

Monitor service is integrated with the site server infrastructure. This integration lets the user specify the resources that each site server monitors.