The coordinator status dialog that appears as part of the coordinator system tray application contains counts of events and alerts. These statistics are periodically recalculated by the coordinator to keep the information as up-to-date as possible.
The event aggreator scheduled task handles the collecting of all incoming agent events. The coordinator receives agent events (batched from the agent) and stores them in temporary storage for bulk uploading to the database. If the bulk uploading has issues (timeouts, etc.), then those events are stored in transaction logs for future uploading. The coordinator can also report to agents that it is too busy (rejects events), which defers the agents from uploading events or allows the agent to send the events to a different coordinator.
The SQL upgrade monitor scheduled task checks to see if any other coordinator is in the process of trying to upgrade. If it finds a different coordinator that is trying to upgrade, it shuts down the coordinator.