Trying to learn how the camera works can be daunting. I teach beginning, intermediate and advanced classes and even though there are only a few settings, the combinations of settings and variables make for a wide variety of options and results. My students often retake classes so they can continue to practice and pick up information they missed the first time around.
This cheat card from Daniel Peters at http://blog.hamburger-fotospots.de/kostenloser-download-foto-cheatcard-fuer-fotografen/ is a good basic start. It shows the basics of how ISO, aperture and shutter speed will affect the picture. Aperture affects how much of the image will be sharp based on where you focus, shutter speeds affects if the image is sharp or blurry and the ISO affects grain in the image. It’s a cool beginning tool all in one diagram.