Previously, targets for Run Command were chosen by selecting instances manually or through tags. With the support of resource groups, you can now select a resource group as the target of Run Command execution. For example, you can patch all of the managed instances that belong in a resource group by executing a Run Command with that resource group selected as the target.
Run Command is a feature of Systems Manager. Systems Manager enables visibility and control of your cloud and on-premises infrastructure. It simplifies resource and application management, shortens the time to detect and resolve operational problems, and makes it easier to operate and manage your infrastructure securely at scale.