Memory and Storage Essentials
Primary storage is what your computer uses right now - RAM for temporary storage (loses data when power's off) and ROM for permanent instructions (keeps data forever). When RAM fills up, virtual memory uses your hard drive as backup RAM, though it's much slower.
Secondary storage is where everything gets saved long-term. You need to know optical CDs/DVDs, magnetic (hard drives), and solid state USBsticks/SSDs storage types, plus when to use each one.
Each storage type has different capacity, speed, portability, durability, reliability and cost characteristics. SSDs are fast but expensive, hard drives are cheap with huge capacity, while optical storage is great for archiving but slow for everyday use.
Units of storage start with bits and bytes, then jump up through kilobytes, megabytes, gigabytes and beyond. Everything in computing uses binary because computers only understand on/off signals.
Memory trick: RAM is like your desk (temporary workspace) while secondary storage is like your filing cabinet (permanent storage) - you need both to work effectively!