If you google cutting horses/loping you will find your answer.. Go to Russ Elrod Cutting horses he explains a lopers job is.. Its to get the edge off the horses before they perform, but theres more to it. A loper is kinda like a groom in the race horse world, with different jobs they have to do. A loper takes care of the horse, they warm them up for the trainers they groom they ice they feed..and I think their jobs are pretty never ending..there is a lot to read up on a lopers job.
My daughter was a loser for awhile. She loved it. In fact, the trainer let her turn back for other people's lessons and even gave a couple for free when some one had to cancel. But I don't know if that is the norm.