Hyper-V Virtual Hard Disk (VHDX)
Definition - What does Hyper-V Virtual Hard Disk (VHDX) mean?
A Hyper V virtual hard disk (VHDX) is a disk image file format used to create a virtual hard disk (VHD) within Windows Server 2012-based virtualization environments.
VHDX enables creating and provisioning virtual/logical disk storage space to virtual machines. It is an enhancement to the previously used VHD file format in Windows Server 2008.
Techopedia explains Hyper-V Virtual Hard Disk (VHDX)
The size/capacity of the VHDX for each virtual machine can be fixed or is dynamically adjusted based on requirements/usage. Although VHDX is not backward compatible, all previous VHD file formats can be converted to VHDX within the Windows Server 2012 OS environment.