The basic unit for a virtual machine (sometimes called a guest machine) is the VMX file. This file contains all the settings needed to build the virtual machine in terms of compute resources, allocated memory, HDD, and networking. Also, it defines the operating system that runs over the machine so the VMware can install some tools to manage the VM powering.
An additional file is needed: VMDK. This file stores the actual contents of the VM and acts as the hard disk for the VM partitions:
These files (VMX and VMDK) should be stored under the /vmfs/volumes/datastore1 directory in the ESXi Shell and should be inside a directory with the name of the virtual machine.