There are two types of booting. they are;-
when power to a computer is given or any special reset signal is given to the computer it is called as cold booting.it first activates the RAM part and then checks the ROM part.it also makes a check on the peripherals wheather they or working properly or not.
when the computer does not respond to the commands given by the user it has to be restarted by clicking restart button or CTRL ALT DELETE KEYS TOGETHER. it makes a check on the peripherals and allows quick reboot.