Anatomy of VM files

                  VMware virtual machine files are organized in the Virtual Machine File System (VMFS).you'll notice that most of the files start with the actual name of the VM, followed by different file extensions that denote the file type. 

 The .vmx file : Configuration file in text format, which means you can open it and read it

                    This file contains all of the configuration information and hardware settings of the virtual machine. Whenever you edit the settings of a virtual machine, all of that information is stored in text format in this file. This file can contain a wide variety of information about the VM, including its specific hardware configuration (i.e., RAM size, network interface card info, hard drive info and serial/parallel port info), advanced power and resource settings, VMware tools options, and power management options.

VMDK files. Disk related files, includes .VMDK, -delta.vmdk, -rdm.vmds

                    All virtual disks are made up of two files, a large data file equal to the size of the virtual disk and a small text disk descriptor file, which describes the size and geometry of the virtual disk file.

                    The different types of virtual disk data files that can be used with VMware virtual machines are:

• The -flat.vmdk file : This is the default large virtual disk data file that is created when you add a virtual hard drive to your VM.
• The .vmdk header file: text descriptor file

• The -delta.vmdk file : These virtual disk data files are only used when making snapshots. When a snapshot is created, all writes to the original -flat.vmdk are halted and it becomes read-only.
• The -rdm.vmdk file :
  This is the mapping file for the raw device mapping (RDM) format that manages mapping data for the RDM device.

The .vswp file. VM's swap file

                 When you power on a VM, a memory swap file is created that can be used in lieu of physical host memory if an ESX host exhausts all of its physical memory because it is overcommitted. 

The .vmss file : virtual machine suspended state file.

                This file is used when virtual machines are suspended and is used to preserve the memory contents of the VM so it can start up again where it left off. 

The .vmsn file : VM snapshot file

                This file is used to store the state of a virtual machine when a snapshot is taken. A separate .vmsn file is created for every snapshot that is created on a VM and is automatically deleted when the snapshot is deleted.

The .vmsd file:  VM snapshot database file

                 This file is used with snapshots to store metadata and other information about each snapshot that is active on a VM. The snapshot information in a VMSD file consists of the name of the VMDK and VMSN file.

.NVRAM -- Consider this file the BIOS of the virtual machine.

When a virtual machine is created and not powered on, these are its files:

When a virtual machine is powered on, these are its files:

When a virtual machine is powered on ans has a snapshot, these are its files: