The difference between colleges and universities is not a purely semantic one. A college and a university are supposed to be different in principle. However, in some countries they may mean the same thing, while in others they may not. Naming things has no absolute rules in all human fields of endeavor.
People familiar with the English language know that words have ambiguous meanings and they may have different meanings according to the context in which they are used. Similarly, when looking at the difference, one has to see the context of the location, where they are situated.
Today the word college is most exclusively used to denote an educational institution, which offers various degree level courses. However, the term can be more widely used, to denote a group of people like an 'electoral college' or a 'college of cardinals'.
As educational institutions, colleges are intermediate stages between schools and universities. There are community colleges in the USA which mostly offer diplomas, certificate level courses and 4 year degrees. One must know how to choose a college, according to one's career interests. In some countries, the terms may be used interchangeably.
The term 'University' is used today to denote advanced institutions of higher learning, offering learning and research opportunities.
Life in a university is more demanding than college life. The difference primarily lies in the number of academic subjects and level of specialization offered at each institution. That's what separates colleges from universities in most countries. However, this may not be the case in every country. In some cases college and university mean the same thing.
In Canada, the difference is quite clear. Colleges offer short vocational course that teach specific kinds of trades. They offer associate degrees in arts ad sciences. The colleges in Canada usually have smaller class size.
The professors are more focused on teaching than research. So in short, Canadian colleges are sort of, intermediate steps between college and university. Universities here offer research opportunities leading to a doctorate.
In UK and Commonwealth Countries
In United Kingdom and most of the countries which are included in the commonwealth nations, the difference between college and universities, is very well-defined. Colleges are subsidiary, specialized institutes of learning under the aegis of a university. A college comes under the affiliation of university.