The last time I’ve tried to run Ubuntu 14.04.02 in VirtualBox, I got a very low screen resolution of 640×480, and xrandr was reporting it’s the only resolution available; not good because I could only use half of each window. This was the first time I came across this issue and don’t really care what caused it, but, searching around the web, I found various possible quick fixes, not of them actually working.
All you need to do is to install Guest Additions. That’s all! ;-)
VirtualBox is a cross-platform virtualization application. Basically, it allows you to run two (or more) operating systems at the same time, on the same computer. This way, you can run a program specifically written for another OS (for example, run Windows software in Linux) without having to reboot your computer.
VirtualBox is available under the General Public License (GPL), which means it’s free, as opposed to it’s rival, VMWare Workstation witch is only freely available for non-comercial use.