Teacher
Teachers in school are those who lecture (US) or teach (UK), give exams and grade students. Teachers in college are called instructors or lecturers.
A teacher who registers a student, or who is positioned to help the student in particular is called a tutor. A teacher or trainer that a student learns quite a lot from may be called a mentor.
The term professor is usually applied (in the US) to college or university teachers that have received tenure, although there are rankings from Associate Professor through Full Professor that may be defined differently at various institutions.
Teachers who look after the whole school are called headteachers. The equivalent in colleges and universities - principals - don't teach. A teacher in a grammar or public school in Britain may also be a Head of House. Houses were also used in secondary and comprehensive schools.
Teachers are usually educated in universities or colleges, and must be certified by a government body to teach in public (U.S.) schools. In the UK, teachers in state schools must have Qualified Teacher Status, either through having done a first degree (such as a BA, BSc or BEd) that leads to this, through doing a PGCE after their first degree, or through on-the-job training at a school.
In traditional China, as the model teacher, Confucius is revered greatly.