It is a comprehensive monitoring solution for collection and analyzing telemetry data
It uses Logs and Metrics collected from the resources for providing insights

For some services like SQL server we need to manually enable auditing and monitoring before Azure Monitor can collect data
For VM we need to install Log Analytics Agent for collecting its data

Azure Alerts can be configured to be sent when certain conditions are satisfied
Azure Monitor Insights can be used to view KPIs of resources

Azure Monitor Overview | Microsoft Learn