Generally a teacher works in a school (or academy as they have recently been called) for 5-16 year olds having compulsory education. As well as teaching they are carers. Colleges and universities have lecturers who are paid on a different pay scale. They lecture and give tutorials. Colleges are generally for 16-18 year olds and are career orientated- both academic and non academic subjects. They are taught by lecturers (academic) or sometimes facillitators. Universities are 18+ and require an entrance qualification. Each department of a university has a professor (maybe more than one I'm a bit out of touch now) who is supposedly an expert on some aspect of her/his subject. She/he will also give some lectures. University lecturers and professors generally also spend time on academic research. This is just a general overview. There are many exceptions to the above.