Azure Resource Manager is the deployment and management service for Azure. It provides a management layer that enables you to create, update, and delete resources in your Azure account. Using it, you can manage your infrastructure through declarative templates rather than scripting. It ensures that all resources in a solution are consistently deployed with a single, coordinated operation. Answers mentioning solely cost management or as a security feature are incorrect, as these are distinct aspects that might be facilitated by ARM but are not its primary role.