Alternatively referred to as boot up, booting is the process of powering on a computer and getting into the operating system. During the boot process, the computer will perform a self-diagnostic, also known as a POST and load necessary drivers and programs that help the computer and devices communicate. As your computer is booting, you may see a screen similar to the example picture below.
In the above example, this screen is displaying the BIOS information, the type of computer, CPU, and memory for the computer and a prompt to enter BIOS setup.
If the computer cannot boot you may receive a boot failure, which is an error that indicates the computer is either not passing POST or a device in the computer such as the hard drive has failed.