Dual booting is a means of installing and using multiple operating systems on a single computer.
These systems are located on separate drives or partitions
an open source program called Grub2, everybody in the world
can dual boot virtually any computer.
Simply put when you switch your
computer on, instead of loading your operating system, Grub2 is loaded
if you have only one operating system installed, it will load
instantly and you will never see Grub2.
If you have more than one
operating system installed, you will be presented with a list of
operating systems you can load.
The first operating system on the list
will be loaded after a few seconds unless you use the up / down arrows
on the keyboard to select another operating system, pressing enter will
then load your choice of operating system.
Grub stands for Grand Unified Boootloader, and is the default boot loader for Ubuntu and many other Linux distributions.
You will have chioce of loading the operating system you want when you switch the computer on.
You can purchase dual boot capable computers.