You use Azure Policy to enforce tagging rules and conventions. By creating a policy, you avoid the scenario of resources being deployed to your subscription that don't have the expected tags for your organization. Instead of manually applying tags or searching for resources that aren't compliant, you create a policy that automatically applies the needed tags during deployment. Tags can also now be applied to existing resources with the new Modify effect and a remediation task. The following section shows example policy definitions for tags.
Reference
https://www.finops.org/projects/multi-cloud-tools-and-terminology/
https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/tag-policies