Teachers are people who teach other people and deal with education. Most often, one thinks of teachers who work with children and young people at a school. But there is also teaching at universities.
There are also swimming teachers or driving instructors. Other teachers do not work at a school, but still teach others. For example, they come to the house and teach how to play the piano.
If you want to become a teacher at a school, you have to study at a university or technical college. There, on the one hand, you learn the content of certain subjects. For example, if you want to become a chemistry teacher, you study chemistry. On the other hand, you also learn how to deal with people and how to teach others. There is a separate science for this, didactics.