The height of the person is influenced by many factors, like good nutrition, onset and end of puberty and, most importantly, by the genetic predisposition. Most people by the time they are 19 have stopped growing and reached their final height. By that age growth epiphyses (the areas of the bones in your arms and legs that grow) have closed and the bone cannot get any longer. Unfortunately, once that happened, there is not much you can do to become taller.
If you have seen advertisements for products that promise to make you taller, beware, there are no pills or devices that can increase your height. Try to remember that height is only on aspect of who you are and that you have many qualities that you can control, like how you are as a friend, how hard you work and how you treat other people.