Welcome to APUG, Squirt! You have asked an important question, and you got good answers here. If you stick with this sort of photography for a while, you will have many more questions about EI, ISO, development times, CI, gradients, and much much more. It may help you to get along this wonderful journey to read up something that will explain it all in a gentle, concise and authoritative way. One of the best such reads is a set of three books by Ansel Adams, titled: The Camera, The Negative, and The Print. Get the more recent editions.

Enjoy, and keep asking questions.