In representations it is usually the attorneys or if somebody is representing themselves, giving an argument about what would be shown as evidence in front of the judge versus an evidentiary hearing which there would actually be testimony and cross examination. 

Most of the time the courts would prefer that it be representations because it is a much quicker process and does not take as much time and the courts calendar can be pretty busy. 

On the other hand, a lot of times people; particularly the defendants in contempt cases they would want to have an evidentiary hearing to be able to get more details out and to be able to cross examine the other side. It is something that you would want to talk to your attorney about before deciding to do representations or have an evidentiary hearing.  If you are requesting an evidentiary hearing, a good practice would be to put that in writing along with your answer to the contempt.