Western saddles come in many styles. The job of a saddle is to disperse the rider's weight over the length of the rib cage which will reduce the pound per square inch to an acceptable level for the horse.  Types of saddles include roping saddles, cutting saddles, reining saddles, team penning saddles, trail riding saddles as well as pleasure saddles. Western saddles generally come in three widths. Semi quarter horse which is a narrow tree, quarter horse which is a medium tree and full quarter horse which is a wide tree. You can purchase saddles with square skirting or round skirting. You may want to choose a round skirt if you have a short backed horse. This will help to make sure that the saddle will not inter-fear with the horses gait. It is also a little lighter in weight. Saddle trees used to be made of wood and covered with bull hide, very strong, but very heavy and they would be very expensive today.  New technology has provided us with fiber glass and resins that are strong and light weight. They provide a good value for the money. Just be sure that you purchase a saddle for your intended use. In other words a trail saddle is generally not made to rope cattle because the horn will not withstand the shock of rope when dallied after a steer has been roped.