RSAT is a set of components for managing a server locally or remotely. When you install a role or feature on a server through Server Manager, it will suggest that you install the Management Tools, or you can install it from Server Manager later. From PowerShell, you can include the
-IncludeManagementTools option on the installation command, or use the
Install -WindowsFeature command to install the Management Tools later.
But if you're running Hyper-V Server only, you don't have this option, as Hyper-V Server doesn't have Server Manager or MMC (Hyper-V Manager). In this case, you can install RSAT, Hyper-V Manager, and Hyper-V module for PowerShell for Windows 8.1 and manage ...