When powering on a computer, the boot device is the hardware that contains the operating system that will be loaded into memory and executed. The computer’s firmware will typically present the user with a list of available boot devices, and the user must select which one to use.
The importance of choosing the correct boot device cannot be overstated. If the wrong boot device is selected, the computer may not be able to boot successfully, or it may boot into an incorrect operating system. It is important to be aware of the different boot devices that are available and to know how to select the correct one.