It takes a minute or two for your computer to turn itself on. This process is called "booting up" because the iMac is actually going inside of itself and pulling itself up by its own bootstraps, so to speak.
Note
software: The invisible programming code that makes things happen inside the computer. You can't touch the software itself. You can touch the disk that stores the software, but you can't touch the code.
Your computer, however, is a piece of hardware; hardware is anything you can bump into.