RAM = The physical chips (Integrated Circuits or ICs) that temporarily store your data as the Pentium (or Pentium-like) chip “crunches the numbers” (processes the data).

Cache = A space on your hard disk set aside to act as “simulated RAM” (especially if you don’t have enough physical RAM). This is much slower than having the actual RAM chips installed, so it is always better to have lots of RAM in your computer. A new computer usually comes with about 512 Megabytes of RAM, which is the minimum you should have nowadays, especially with the second version of Windows XP (“Service Pack-2”). [Actually, it's the third version.] Ideally, you should now have about 1,000 Megabytes of RAM or more.

Hard disk = a component inside your computer that's about the size of a small Bible with a disk about 3 inches (or less) inside its case. The disk spins at about 5,000 rpm or more and is coated with iron oxide particles that store a magnetic charge. There are tiny “pickup heads” that swing across the surface of the disk, picking up the magnetic charges (very quickly) and translating them into your data and programs. When you hear the low grinding noise coming from the tower or from inside your laptop (and see that green or red light blinking occasionally), this is caused by the pickup arms moving around, reading the surface of the disk.