I'm pretty sure its a timed ride cross country with jumps. I don't think the jumps are that big, I also think they may be optional but I'm sure someone more experienced than me can correct me on that point.
As I understand it, you can participate as a single or on a team and the single or team closest to the optimal time wins.
At least that is what I vaguely remember. I took a few lessons at a local barn before the cold weather hit and the trainers daughter does them. So when I start up again in the spring, I think that will be a goal. :)