Who is the teacher? What is the teacher?
Some good teachers teach the good things and uplift the students' lives. On the other hand, bad teachers teach the bad things and down the students' lives.
One point is that Good teachers teach the Good Professionals for Good Life.
On the other hand, Bad teachers teach the Bad Professionals for Bad Life.
Anyway, the role of the teacher is never be replaced. In our country, Good teachers are regarded by the respected role as the parents.
Most of the people tell that the person who teaches in the classroom is the teacher.
On the other hand, the parents teach their babies and children before they go to the school (As an example, how can eat, how can drink, how can wear,...)
Some people also tell that their teachers are not humans like the books, the educational videos, websites, etc.