During my bachelors and masters degree I have attended some brief talks called colloquiums in which a researcher was invited by a professor at the university and s/he gave a one-hour talk about a scientific topic most of which about his/her own research interests.
These talks are a little different from normal conference presentations and seminars because the speaker is invited to give a talk and he is not presenting a specific paper; but in a conference, except from keynote speakers; people normally submit their papers to be peer-reviewed.
I don't know what's the role of colloquiums in academia and what the speaker is seeking by giving such talks? Also, who can give such talks (a researcher, somebody from industry, an outstanding professor, etc.)?