Portability - VirtualBox runs on a  large number of 32-bit and 64-bit host operating systems. VirtualBox is a  so-called "hosted" hypervisor (sometimes referred to as a "type 2"  hypervisor). Whereas a "bare-metal" or "type 1" hypervisor would run  directly on the hardware, VirtualBox requires an existing operating system  to be installed. It can thus run alongside existing applications on that  host. To a very large degree, VirtualBox is functionally identical on all of  the host platforms, and the same file and image formats are used. This  allows you to run virtual machines created on one host on another host with  a different host operating system; for example, you can create a virtual  machine on Windows and then run it under Linux. In addition, virtual  machines can easily be imported and exported using the Open Virtualization  Format (OVF), an industry standard created for this purpose. You can even  import OVFs that were created with a different virtualization software.

No hardware virtualization required  - For many scenarios, VirtualBox does not require the processor features  built into newer hardware like Intel VT-x or AMD-V. As opposed to many other  virtualization solutions, you can therefore use VirtualBox even on older  hardware where these features are not present.

Guest Additions: shared folders, seamless  windows, 3D virtualization - The VirtualBox Guest Additions are  software packages which can be installed inside of supported guest systems  to improve their performance and to provide additional integration and  communication with the host system. After installing the Guest Additions, a  virtual machine will support automatic adjustment of video resolutions,  seamless windows, accelerated 3D graphics and more. 

In particular,  Guest Additions provide for "shared folders", which let you access files  from the host system from within a guest machine.

Great hardware support - Among  others, VirtualBox supports:

• Guest multiprocessing (SMP) -  VirtualBox can present up to 32 virtual CPUs to each virtual machine,  irrespective of how many CPU cores are physically present on your host.

• USB device support - VirtualBox  implements a virtual USB controller and allows you to connect arbitrary  USB devices to your virtual machines without having to install  device-specific drivers on the host. USB support is not limited to  certain device categories.

• Hardware compatibility -  VirtualBox virtualizes a vast array of virtual devices, among them many  devices that are typically provided by other virtualization platforms.  That includes IDE, SCSI and SATA hard disk controllers, several virtual  network cards and sound cards, virtual serial and parallel ports and an  Input/Output Advanced Programmable Interrupt Controller (I/O APIC),  which is found in many modern PC systems. This eases cloning of PC  images from real machines and importing of third-party virtual machines  into VirtualBox.

• Full ACPI support - The Advanced  Configuration and Power Interface (ACPI) is fully supported by  VirtualBox. This eases cloning of PC images from real machines or  third-party virtual machines into VirtualBox. With its unique ACPI power  status support, VirtualBox can even report to ACPI-aware guest operating  systems the power status of the host. For mobile systems running on  battery, the guest can thus enable energy saving and notify the user of  the remaining power (e.g. in full screen modes).

• Multi-screen resolutions -  VirtualBox virtual machines support screen resolutions many times that  of a physical screen, allowing them to be spread over a large number of  screens attached to the host system.

• Built-in iSCSI support - This  unique feature allows you to connect a virtual machine directly to an  iSCSI storage server without going through the host system. The VM  accesses the iSCSI target directly without the extra overhead that is  required for virtualizing hard disks in container files.

• PXE Network boot - The  integrated virtual network cards of VirtualBox fully support remote  booting via the Preboot Execution Environment (PXE).

Multigeneration branched snapshots -  VirtualBox can save arbitrary snapshots of the state of the virtual machine.  You can go back in time and revert the virtual machine to any such snapshot  and start an alternative VM configuration from there, effectively creating a  whole snapshot tree.You can create and delete snapshots while the virtual  machine is running.

VM groups - VirtualBox provides  a groups feature that enables the user to organize and control virtual  machines collectively, as well as individually. In addition to basic groups,  it is also possible for any VM to be in more than one group, and for groups  to be nested in a hierarchy -- i.e. groups of groups. In general, the  operations that can be performed on groups are the same as those that can be  applied to individual VMs i.e. Start, Pause, Reset, Close (Save state, Send  Shutdown, Poweroff), Discard Saved State, Show in fileSystem, Sort.

Clean architecture; unprecedented modularity - VirtualBox  has an extremely modular design with well-defined internal programming  interfaces and a clean separation of client and server code. This makes it  easy to control it from several interfaces at once: for example, you can  start a VM simply by clicking on a button in the VirtualBox graphical user  interface and then control that machine from the command line, or even  remotely. 

Due to its modular architecture, VirtualBox can also  expose its full functionality and configurability through a comprehensive  software development kit (SDK), which allows for integrating every aspect of  VirtualBox with other software systems. 

Remote machine  display - The VirtualBox Remote Desktop Extension (VRDE) allows for  high-performance remote access to any running virtual machine. This  extension supports the Remote Desktop Protocol (RDP) originally built into  Microsoft Windows, with special additions for full client USB support.

The VRDE does not rely on the RDP server that is built into Microsoft  Windows; instead, it is plugged directly into the virtualization layer. As a  result, it works with guest operating systems other than Windows (even in  text mode) and does not require application support in the virtual machine  either..

On top of this special capacity, VirtualBox offers you more  unique features:

• Extensible RDP authentication -  VirtualBox already supports Winlogon on Windows and PAM on Linux for RDP  authentication. In addition, it includes an easy-to-use SDK which allows  you to create arbitrary interfaces for other methods of authentication.

• USB over RDP - Via RDP virtual  channel support, VirtualBox also allows you to connect arbitrary USB  devices locally to a virtual machine which is running remotely on a  VirtualBox RDP server.