What do letters ROM stand for?

RAM stands for Random Access Memory or memory in your computer that can be read and written to by programs. The amount of RAM in a computer has a bearing on how much work it can do in a given amount of time, and how complex a program that can be run. The other type of electronic memory in a computer is called ROM, or Read Only Memory, and is the kind of memory that is programmed permanently at the factory that makes your computer a computer and not a toaster. ROM is fixed and usually a smaller size, RAM is expandable (to a point).