There is a special kaddish that is recited at the graveside and at a siyum, a celebration for concludign learning a large portion of Torah. This kaddish is unique because it is unusually long and contains some tooth-breaking Aramaic. Why is this kaddish so different from all other kaddish texts and why do we say it at these two occasions?
R. Ya'akov Kamenetsky (Emes Le-Ya'akov, Shulchan Arukh, Yoreh De'ah 246:10 n. 130) explains:
The kaddish we recite at a siyum and at a burial do not have anything more than the usual kaddish. However, since there are so many ignorant people at a siyum and burial, they translated and explained the text of the kaddish [in Aramaic] so that they will also understand it.