It is. Representation Of Memory, or ROM, is a technique used in computer architecture to significantly increase the speed of computers.
In a nutshell, computer architecture indicates that data stored on a disk will always take longer to read from than data stored in RAM (read-only memory). In other words, it takes much longer to retrieve information from a disk drive no matter how fast the processor. While there are certainly some steps taken by hardware vendors and software engineers to make disks faster, nothing can really compete with RAM when it comes time for pure speed.