Historically, a college was a place where people came together for a specific purpose.

That purpose did not have to be educational, as in the College of Cardinals, or the College of Arms.    But most colleges today have a primarily if not exclusively educational purpose.

Chambers Dictionary defines college as “an institution for higher, professional or vocational education."

In higher education, colleges tend to be parts of universities, as at Oxbridge, London or Durham.    This division is not by subject (as in departments or faculties) but based on governance, finance, geography, or just historical accident.

In further education a college is more like a university:  a self-standing autonomous body.    Most state-funded bodies offering FE courses are called Colleges.    And certain professions tend to train at colleges, such as in medicine, music, theology and the technologies.

All these colleges offer education beyond or after school, as the phrase “going to college” implies.

But a few schools are also called colleges, like Dulwich or Eton, again for historical reasons.

Colleges were commoner in the past.    Distance learning providers were called correspondence colleges, and many bodies used the term in their titles; ODL QC was originally the Council for the Accreditation of Correspondence Colleges.

Some private sector providers still call themselves colleges, though the proportion is small; probably less than 20%.

There are no restrictions on using the name, and often little difference between those who call themselves colleges, and those who choose school, academy, centre or whatever.

The choice of name has no implications for what they offer, or how good it is.   But it does have academic associations.    Some providers call themselves colleges if they want to project an academic image.

Those who wish to avoid such associations, avoid the word.    So those who offer courses to industry and commerce are more likely to choose centre, company, or training organisation instead.