If the html changes depending on whether it's a spider or a surfer, then that's cloaking.
If you have an h1 tag that is covered up by an image (eg absolute positioning or a div with an image background that is the same colour as your h1 test), but the html is still the same for both spiders and surfers, that's not cloaking. However you are still hiding content in a semi-dodgy manner and that can still get you in trouble if your site gets manually reviewed.