Understanding the meaning of terms such as Aperture and Shutter Speed is essential for full control of your photos. Knowing when to use what value can mean the difference between an average shot and an amazing one. Canon’s Exposure Simulator is an excellent resource to learn just that.
Learn the basics of exposure. The simple and easy to understand tutorials are great at understanding what different aperture values do. See how a fast and slow shutter speed can affect motion in a photo. And what ISO sensitivity does.
The simulator allows you to adjust settings found on DSLRs and other cameras. You can actually snap photos and see how you did.