Well, whenever you're on a good website that mentions Macromedia Flash, that's what it can do. Jeff's site is made using flash. It's good for transitions, moving stuff around the screen, interactivity, coding just basically tons of stuff. It takes a while to master but when you do you can do pretty much anything, you might also want to look into Macromedia Director which is a slightly more hardcore version, probably more used for making really professional presentations and interactive multimedia.