Azure Monitor is a service that delivers a comprehensive solution for collecting, analyzing, and acting on telemetry (metrics and logs) from your cloud and on-premises environments.
These logs differ from the activity log. The activity log (previously known as audit logs) provides insight into the operations, such as creating a VM or deleting a logic app, that Azure Resource Manager performed on resources in your subscription using. The activity log is a subscription-level log. Resource-level diagnostic logs provide insight into operations that were performed within that resource itself, such as getting a secret from a key vault.