I had a good friend who was really into horses and horse training, but I dont personally know anything about it, do you?
Yes I know quite a bit about horses. They are trained for a variety of different things such as everyday care, and horse racing. 
Yes! Also like they are trained to go over jumps and stuff too!
Yes today horses and usually trained towards sporting pursuits but historically it was much different. 
Right, as in they were used for transportation back in the old days? Like pulling wagons?
Yes that was one thing, they used to be used for transport, doing farm work and they were heavily used in warfare. 
warfare??? I know people rode them but what else did they do in warfare? I hope they didnt get hurt by people
When horses were trained for warfare some horses even contributed in the fighting. One example are armored horses that would trample the enemy. 
Oh my, that sounds awful. I would not want to be one of those soldiers!!
Horses were first used in battle over 5000 years ago and they were doing it for thousands of years.