A clone is a new VM that is a copy of the original. It will create exact copy same as you copy and paste other files and inside content remained same.
A snapshot is a backup of a point in time for that VM, the snapshot allows you to restore to a point in time to the same VM. For example - if you take a snapshot before you change the VM, ie. windows updates, application install, config changes, etc and find that you now are unable to run the VM, you can revert to the snapshot, like it never happened.
A Template is a copy of pre-installed VMs containing all the software and configuration settings that would make the VM work when deployed. With this single image you deploy multiple VMs again and again.
