Guest Additions are very useful in VirtualBox (or any other virtualization software in general), it installs virtual adapters for your hardware and enables the following:

• Better graphics support (very useful when resizing the desktop or changing the guest’s resolution)
• Folder sharing between the host and the guest (you can refer to this article for a how-to)
• Mouse Integration

Maybe other features as well which I don’t know. To install the guest addtions, you can simply follow the following five steps:

1. Click Devices->Install Guest Additions, this will mount a virtual cdrom containing the files from which we will install the guest addtions.
2. Open a terminal and navigate to the folder containing the guest additions “cd /media/cdrom”
3. Run the guest addition installer “sudo sh VBoxLinuxAdditions-x86.run”
4. Wait till the additions are installed and the kernel modules are compiled, note that this may take a few minutes.
5. Restart the Ubuntu guest.

This article is dedicated to my cousin Midoooz, to use it in his first virtual machine 🙂