What you normally have to do is ride around the ring as a ride, then line up, each horse then comes out and does an individual show, at higher level shows tack is taken off to see conformation without saddle on. And at the higher level you will also have a ride judge who will ride your horse to assess rideability. As far as what types, see the link below which shows a classic ridden hunter: http://www.thisisdevon.co.uk/Ridden...championship/story-11421731-detail/story.html though at some shows you may have more sub divisions such as small hunter, lightweight hunter, heavyweight hunter and working hunter, the types of horses in each of these sub divisions varies and it's best just to google them and see the type.
sorry forgot to say, the individual show should demonstrate the horses ability to walk, trot canter on each rein and show a controlled hand gallop, if you can do extra like rein back at the end etc all the better. But the whole individual show shouldn't take long. Baring in mind there can be at higher level shows up to 20 horses in the class! The judge will get bored if it takes too long.
Its very rare for any of the horses to be ridden at most of our local shows, so don't worry too much about that. For some reason, its also a class that seems to attract broncos at our local rc too!
Basically its just a heavier type of horse, suitable for hunting, think irish draft type. You will ride as a group, in trot and canter, and the judge will be looking for a nice horse with good manners (ie brakes) and paces etc. The horses will be lined up - may be in order, may not, then do an individual show, which should include an extended canter.