Basically, you take an aerobatic airframe and put 2 1/2 to 3 times thrust to weight and go "flying". I had the joy of watching a freestyle competition at an IMAC meet at a local field last summer. I have not tried 3D myself, but it is truly fun to watch and the pilots are very skilled. Ive seen 40% planes take off with a 2 foot run and go straight into a hover no more than 10 feet off of the ground. Some of the maneuvers just leave you shaking your head and saying "theres no way an airplane should do that", lol. Do a google search for 3D R/C aerobatics and check out some videos.