What's the difference between regular (aka full), position and short papers? I've sent the article to the conference and it has been accepted. However, I received a message that my paper has been accepted as the short paper. 

I know that there's a difference in, for instance, the oral presentation time between those 3 kinds of papers. However, I wonder if the type (regular, position, short) can say anything about the quality or the importance of the paper's subject?
Here is what I have observed at the peer-reviewed conferences that I attend:


A regular full paper is your basic standard peer-reviewed paper.  
A position paper is for ideas that don't have and results, per se, but are worth communicating to the community, or for announcing a result that has been published with another community.
A short paper is for work that is worth publishing, but doesn't rise to the level of quality or significance of a full paper.


Short papers are generally significantly less respected than full papers, but may be worth it anyway: a short paper in a high-profile conference is often better than a full paper in a less significant conference.  Position papers are funny and in a different category: they aren't attempting to be the same as a full paper, and are typically judged more by a standard of "interesting to discuss."