Printer carrier jam error

What are the causes for a carrier jam problem on a printer? I mean, I'm looking for documentation that explains this. All explanations I've got (which have been varied and sometimes too ambiguous) have come from people in forums, etc. So, I believe if I could get this info from a more reliable source (like an article, manufacturer document/white paper, etc.) it would be best.

Can anybody point me in the right direction?

Thanks!