This document discusses different types of storage devices used in computing. It identifies primary storage devices as those that are part of the computer like RAM and ROM, which are needed for the computer to function. Secondary storage devices include removable media like hard drives, optical disks, magnetic disks, and USB drives that can store information both internally and externally. The document defines different types of optical disks such as CDs, DVDs, and Blu-ray disks, and their uses for permanent or temporary storage. It also discusses the differences between volatile and non-volatile memory.