|Single boot means having only one operating system (OS) installed on your computer..|
Dual booting refers to having two OS's installed on your computer. Correctly done, a person can boot to either OS utilizing a "boot manager" that allows you to choose between available OS's. Pretty much all the NT based windows OS's, Linux and UNIX have boot managers built into them.
One can also have more than two OS's installed on a single PC and boot between them,
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.