The Kaddish prayer is one of the most important and well known Jewish prayers. However, Kaddish can be confusing, there are many different types of Kaddish said on different occasions and at different point during the prayer. Some Kaddish are said only by the cantor while others are said by mourners. 
A fascinating discussion about the Kaddish prayer, it's history, connection with death and clarity on where and when each kaddish is said.