Learning More About Knights

I would like to learn more about knights in medieval Eroupe. First i would like to learn is what it took ti be a knight. Did you have to be strong , brave, quick, or buff. I think you would have to have all these quilitys to be a knight. Also what would happen to them if got toss off their horse in battle. Would they die or will they surrive. Third is how long did you have to train to knight in medieval Eroupe. these are the things I still want to learn about knights.