Besides a superb graphical user interface, VirtualBox has a command-line interface which can be run from a command line or terminal session. You have to navigate to the installation directory for VirtualBox. On Windows 7 it is located in
C:\Program Files\Oracle\VirtualBox

Once in the directory, you control the virtual machines by using the vboxmanage command followed by a subcommand, followed by the name of the VM that you want to work with.  
Examples: 

List the currently configured VMs.  
 vboxmanage list vms

“UbServer1” {86742a7d-1188-4b48-b09a-4a0139d14930}
“UbServer2” {30bbee61-7115-4494-91fb-987a1dad74a4}
“UbDesktop” {a83379da-31e4-4064-b4c7-de4dec73195d}
“RHServer71” {bf9515d0-aead-4423-990b-3a6493712dc0}
“RHDesktop” {461c94b9-6743-4d7b-a444-6972586a562b}

This shows that I have 5 configured VMs…. two Ubuntu servers, a Ubuntu desktop, and two RedHat virtual machines.

To find out information about a specific VM:

vboxmanage showvminfo ubServer1

Name:            UbServer1
Groups:          /
Guest OS:        Ubuntu
UUID:            86742a7d-1188-4b48-b09a-4a0139d14930
Config file:     C:\Users\Larry\VirtualBox VMs\UbServer1\UbServer1.vbox
Snapshot folder: C:\Users\Larry\VirtualBox VMs\UbServer1\Snapshots
Log folder:      C:\Users\Larry\VirtualBox VMs\UbServer1\Logs
Hardware UUID:   86742a7d-1188-4b48-b09a-4a0139d14930
Memory size:     2048MB
Page Fusion:     off
VRAM size:       12MB
CPU exec cap:    100%
HPET:            off
Chipset:         piix3
Firmware:        BIOS
Number of CPUs:  1
PAE:             on
Long Mode:       off
Synthetic CPU:   off
CPUID overrides: None
Boot menu mode:  message and menu
Boot Device (1): Floppy
Boot Device (2): DVD
Boot Device (3): HardDisk 


This is the beginning of the listing, which runs about five screens. It includes all of the information shown in the GUI Settings pane, as well as additional information. 

vboxmanage startvm RHDesktop

Waiting for VM “RHDesktop” to power on…
VM “RHDesktop” has been successfully started.

This starts a named virtual machine.
The counterpart for stopping is:

vboxmanage controlvm RHDesktop poweroff

 Full manual is here