We seem to use the term "intern" for a lot of different categories. I think in Canada, according to the CAFCE guidelines, there's a pretty clear definition. But, when I look at all the different situations that interns wind up in, I wonder if we're doing a favour for students and employers, let alone ourselves the practitioners, in letting loose the many different interpretations.
My most prominent (negative) image and the one which I like to have you imagine least, is the intern in the U.S. television/motion picture industry. Time was that the interns in these roles were compensated and given challenging, productive opportunities. I think those same challenges may still be there, but they've let themselves slide down the slippery slope, greased by the demand from the students and the abundance of roles, to the point where students are not paid. When that happens it means that the engagement of and by the student is lessened. Following this to the logical conclusion, the employer does not see the need to have a student work (and learn) in their workplace if they're not engaged. There are likely many flavours to this story, but I'm describing the most bitter tasting one.
Interns can contribute to their employer post-graduation, pre-graduation, and any number of different ways. Internships often mean that a student is working more than the usual four- or eight-month terms. It's often 12- or 16-months. I think these are very good for the employer and moderately so for the student. It has to be managed well. Ideally the student is progressing through a cycle of roles in that time span. The point being to engage them in all different ways so as to enable them to contribute best and learn optimally. Obviously this is more the case for a series of four-month work-terms...where different employers/supervisors are involved.
This is not meant to be an extensive categorization of what it means to be an intern.
When you hear "intern", be open to the different interpretations.