Jan, take your camera, put it on ISO 200 and f/8, and go take some photos. All of these masses of questions you're asking right now are utterly pointless because the best way to answer them is to learn yourself, and the only way you're going to do that is to go out and take photos. You'll learn precisely nothing by asking questions like these because you need a practical knowledge of how your camera works, not a theoretical one. Seriously, just go take some photos and it will all start to become clear!
