I am guessing it is to warm up their tendons.
Yes it is nessasary to pull the horse forward because it gets rid of skin folds under the strap that can cause wounds to your horse!!!
The pommel on a saddle is the front arched area above the tree. It is more accurately located in front of the seat and it is there to give the horse's withers and scapula room to move freely when being ridden and to keep the rider from sitting too far forward.
A saddle embolus, or saddle thrombus, is a blood clot in the distal aorta. It is called a saddle thrombus because it often blocks on or both of the femoral arteries, sitting like a saddle on the split between the two.
Crupper
To avoid skin folds under the strap that can cause wounds.
It is called the crupper.
it depend on what tyoe of riding your doing. for example if your galloping towards a barrel u sit forward in your saddle but if ur riding a cow horse us sit balanced on the back of your saddle to have more controlfor English riding:for all: you shouldn't be either leaning too far forward, or back. your shoulder should be lined up with your healwalk, you should be relaxed, but still alert and sitting in about the center of the saddle.trot: for a post you lift your butt out of the saddle when your horse rises - you come slightly out of the saddle, not straight up, but slightly forward.canter: as my old trainer desctribed it to me: you kind of "scoop" with your butt.gallop: there is a position called half seat were you lift your butt slightly out of the saddle so its easier for your horse to move faster, if you do half seat instead of sitting down, you will find that your horse is more willing to go faster.jumping: "2-point" its where you lean forward in the saddle (butt up in the air) with a strait back. only go up into 2-point when you feel your horse jump, if you do it to early, your horse may take a little dive before the jump and it will feel kind of akward (trust me). and if you are jumping small fences (2-2 1/2ft) you should stay in the 2-point position for a stride afterthat's about it :o)~Bella
It's so that your rear doesn't fly out of the saddle wile in flight. (Dressage saddles have even higher 'backs' so that you don't bounce as much in the sitting extended trot).
this site tells you exactly how http://www.wikihow.com/Tack-up-a-Horse or.... carry your saddle over to your horse put the numnah or saddle pad on the horses back put saddle on the saddle pad move the saddle forward until the girth is just behind the front legs tighten the girth on both sides pull dwn the stirups and get on and ride. lol. :)
To preform the sitting trot you should already have been riding at a posting trot and developed a good sense of balance. Begin by sitting deeply but lightly in the saddle with your weight in the balls of your feet and lightly wrap your legs around the horses barrel. As the horse trots try to let your ankles and knees absorb the impact but not bounce. You should be able to stay steady in the saddle enough to do a sitting trot.
There are a few things you can do. Check with your local saddle shop as there are saddle pads that are made thicker. You can also double your pads making sure they don't slide around. Your pad may not be forward enough to raise your saddle so that it does't rub. Or the problem may be the saddle. It may be to wide for your horse, therefore it is not sitting on its back correctly. I had two different saddles for this reason. The fork where the horn is attached was higher on one saddle than the other. This gave more room for the withers. If you can check with someone in your area who knows saddles and horses well. Check out some site that offering saddle pad. One of them is http://www.saddleonline.com having many variety of saddle pads.
Cowboys needed a saddle that was comfortable to sit in and work in because they're sitting in that saddle from dawn til dusk. They also needed a saddle that they could rope and herd cattle in, as well as something that was comfortable (relatively speaking) for the horse to wear on his back all day.