Most often in windsurfing you'll progress to the point where you want to experience jumping. A small jump is termed the chop hop, which is the first step towards airtime. The chop hop can be done on flat water but it's easier when there is at least some chop, hence the name.
The chop hop is pretty much like doing the arlie on a skate board, but for those who haven't done skateboarding, here's a better explanation on how to get chop hopping like a pro.
First, you need to be planing and powered up. You also need to learn in chop and not swell, which is different to chop. A swell is almost like a mini hill, large and round, it has no steep face and if you plan to launch off swell it's for big air and not chop hopping. Small steep chop is perfect and takes less energy than doing it in completely flat water.
Look out far ahead and target a steep piece of chop heading towards you. Not too far downwind and not too far upwind, just aim straight on. Unhook and make sure you're not over sheeting at this point. Stand slightly more upright and keep your body light at the same time by bending your legs.
As you approach the chop bend your legs a little more and just before it hits your front foot, lift your front foot and then stomp on the back of the board bringing it up to touch your arse. The stomp part has to be fast and immediately right after you lift your front foot. Don't lift your front foot and back foot at the same time. So, as the chop hits your front foot you lift your front foot and then with your back foot you stomp and lift your back foot. You'll be airborne for a short while... ahhh!
When landing, don't lean too far forward or too far back, just be slightly upright to land planing. Do not over-sheet as this will cause you to spin out when landing.