ROM stands for Read Only Memory. Your computer ROM holds crucial instructions needed for your computer to boot up and operate and can sometimes be referred to as the ”operating system for the operating system”.
ROM is hard-wired into a computer and cannot be changed, hence the read-only moniker. Also, when you turn your computer on and off, the instructions inside ROM do not get erased. Both make ROM different than RAM. Unlike ROM, RAM can be written to, yet it will get erased whenever the computer restarts.