Below listed are the files that makes up a virtual machine in VMware vSphere. It is not necessary that you will see all the files listed below when you create a VM. This is because, some files will come in picture only when you perform certain operations on a VM. For example, If you take a snapshot of VM, then you will see snapshot related files in VM folder.
There are few other files also get created such as .ctk (Backup Tracking file for backup jobs) or .lck (NFS lock file if VM is placed on NFS datastore) if related operations are performed.
As per recent update, there is new addition of .vmem file for holding memory state (content of RAM) while doing snapshot operation on a running VM. This is optional though, as you need to select whether you want to include RAM content or not.
Another file to look at would be rdm.vmdk in virtual mode RDM mode and rdmp.vmdk in physical mode RDM.