Kite boarding is a sport where you take a giant, 10+ meter wide kite, connect it to your chest with a harness, then step onto a large board (think boogie board size, not surf board) and have the wind pull you at speeds that can exceed 55 mph (50 knots, 90 km/h ). If you are a beginner/taking lessons, you might take a boat off shore to where it is easy and safer to start. But good kiters can start from the beach.
It is expensive, difficult and hard on the body. It doesn't take a huge amount of muscle, but it does take a lot of stamina. You can't just take it easy when you get tired - particularly if you find yourself out a mile off shore. How fast you go depends more on the wind speed than on how hard you want it. In most sports the difference between a pro and an amateur is just as much about willing to give it your all as it is about how much your "all" is. Not so with Kite boarding - you have to give it your all, or quit, at least when you are a beginner. As you get better you use less muscle and flow with the wind, rather than fight it. In addition it is a full body workout - legs, back and arms. As such, if you aren't young, healthy, and in shape, be prepared to be totally exhausted by lunch time - as in lie down and take a nap. I did.
It is also rather expensive - it's not just the gear: board, floating sunglasses, kite, ropes, harness and pump (the kites have inflated tubes on the edges to hold the right shape). You need a water resistant shirt (not cotton) to protect your chest from the harness and sunburn. I liked having water shoes on my feet - particularly when on a rocky beach area. You will definitely need some classes to start at the very least. There is also the travel. Not everyone lives near appropriate locations and the wind is fickle. Finally you may need to pay someone with a boat to hang out and/or save you if the wind doesn't cooperate.
That said, it is a TON of fun. I tried it in water, but you can also try it on snow (snow kiting). Obviously summer water is warmer than snow, but you have to do more work - it's harder to start it up as the board goes under the water and you have to hold it in the right shape to start. Snow kiting is less work to for that reason, if a bit colder. Also, your head doesn't go under water, which for some people is a big plus.
Jumping is fun - but if the wind picks up suddenly you may find yourself trying it out before you are ready. Experience people can do a ton of interesting tricks - my teacher would literally jump over small island reef that had a a bonfire set up on it. It was pretty amazing site.
It's more male than female - say 2 men for every woman. It's hard but not impossible to take it up after 40 - the stamina issue. Mostly 30's - 20 year olds don't have the money/time, aside from the professional teachers. But if you have the money, a teenager can easily do it.
I took kite boarding lessons on vacation at the "Pro Center Kiteboarding School", Union Island, in the Grenadines. http://www.kitesurfgrenadines.com. The wind there is near constant 24/7, 365 days a year. If you go during the prime season, it can be a fun party.
But it is a long trip (near Venezuela) and requires you to fly in on a small aircraft, so it is not easy to get to. There are a lot more convenient places, including Cape Hatteras in North Carolina. http://www.realwatersports.com/capehatteras