You create resource mappings between the vRealize Automation catalog resource type and the vRealize Orchestrator inventory type to manage resources provisioned outside of Advanced Service Designer.
For example, you might want to create an action so that users can take a snapshot of their Amazon machines. For this action to work on an Amazon machine provisioned by using IaaS, the three components involved, Advanced Service Designer, vRealize Orchestrator, and IaaS, need a common language for the Amazon machine. You create that common language by adding a resource mapping in Advanced Service Designer that runs a vRealize Orchestrator scripting action or workflow to map the IaaS Cloud Machine resource type to the vRealize Orchestrator AWS:EC2Instance inventory type.
vRealize Automation provides resource mappings, and the underlying vRealize Orchestrator script actions and workflows, for vSphere virtual machines, vCloud Director virtual machines, and vCloud Director vApps.