There is only one file type that uses the .VMXF extension:
VMware Team Member File
Additional configuration file used by virtual machines (VMs) created with VMware virtualization software; contains team member data for VMs created in a team group environment, a setup that allows administrators to manually control multiple VMs together; created in addition to the primary .VMX configuration file; saved in a plain text format and uses XML formatting.
NOTE: You do not need to manually open VMXF files since the VMware software handles them behind the scenes while you configure VMs.
Updated: April 15, 2012