Do you already think you know this? Just stick your camera in auto-focus and click away? There's a lot more to photography than just taking photos. Take the time to read Brian Dilg's in-depth article of how modern camera lenses work, and how to use them to your advantage. It just might make you an even better photographer.
Brian Dilg writes:
Yes, modern lenses are ultra-sharp and super-contrasty, they focus automatically, and undesirable artifacts like chromatic aberration and barrel distortion have improved. However, autofocus technology has brought three critical changes that serious photographers need to consider carefully when they choose their lenses, because they can be a hindrance to thoughtful photography if not used carefully.