Internal

Networking

VirtualBox Networking Concepts

The "current state" represents the "now" point in the life time of the virtual machine. The current state can be preserved by taking a snapshot.

A clone that copies all depending disk images into the new VM folder. A full clone can fully operate without the source VM.

A linked clone refers to parent disk images.

If "Everything" is chosen when cloning, the current state of the VM and all snapshots are cloned.

A snapshot contains the current state of the virtual machine, which consists of:

the complete copy of the VM settings, including the hardware configuration.
the complete state of all virtual disks attached to the VM. Going back to a past snapshot means that all changes that have been made since the snapshot has been taken will be discarded.
if the snapshot was taken when the machine is running, the memory state is preserved as well.

The procedure to restore a VM from a snapshot is available here:

Restoring a VM from a Snapshot