It is like a digital memory for your computer. You have bytes of information… then KILObyte- roughly 1000 times bigger value then one byte… then MEGAbyte- roughly 1000 times bigger value the one kilobyte… then GIGAbyte- 1000 times bigger value then one megabyte… then TERAbyte- 1000 bigger value then one gigabyte.
Same story with watts – KILOwatts – MEGAwatts – GIGAwatts – TERAwatts. Tricky metric system 🙂