Hop turns are without a doubt a challenging manuver to execute. They are characterized by a 180 dergee rotation/turn that is executed in the air via hopping motion. The purpose of the hop turn is to make quick direction changes on extremely steep terrain often in tight spaces (many times when approaching a cliff or narrow chute when you want to control your speed.)
They are a crutial step to becoming a well rounded expert skier. The key when learning is to make sure that you rotate fully and come to a complete hault between turns. under rotation will cause the skis to track down the hill and you will lose control of the turn. The best place to learn hop turns is on a moderately steep, groomed slope. go somewhere that is not crowded.
begin with your skis horizontal to the falline with your downhill pole planted in the snow. the first movement is an exploision from the core and upper leg muscles. use your planted pole to assist your body and skis in leaving the snow. rotate your skis 180 degrees around your planted pole and land solidly with a pole plant (new downhill pole). once you have executed the move, it should be a fluid motion: hop>stop>plant hop>stop>plant directly down the falline of the slope in a straight line. once you can do this with ease, you will be able to ski through all kinds of terrain, including narrow chutes and tree skiing.
hope you can follow, let me know if you need any more advice, i am an NCAA All-American and I have been skiing skince i was 2 and competing since i was 7 yrs old.