Mourners Kaddish
The Kaddish is a prayer that praises God and expresses a yearning for the establishment of God’s kingdom on earth. The emotional reactions inspired by the Kaddish come from the circumstances in which it is said: it is recited at funerals and bymourners, and sons are required to say Kaddish for eleven months after the death of a parent.
The word Kaddish means sanctification, and the prayer is a sanctification of God’s name. Kaddish is only said with aminyan (prayer quorum of ten men), following a psalm or prayer that has been said in the presence of a minyan, since the essence of the Kaddish is public sanctification. The one who says Kaddish always stands. Whether other worshippers sit or stand depends on the congregation. It is customary for all the mourners in the congregation to recite Kaddish in unison. A child under the age of thirteen may say the Mourner’s Kaddish if he has lost one of his parents. Most religious authorities allow a daughter to say Kaddish, although she is under no religious obligation to do so. The Mourner’s Kaddish is recited for eleven months from the day of the death and also on the yahrzeit (anniversary of a death). A person may say Kaddishnot only for parents, but also for a child, brother, or in-law. An adopted son should say it for adoptive parents who raised him. The Rabbinical Kaddish, Half Kaddish, and Whole Kaddish may be said by a chazzan (cantor – prayer leader) who is not a mourner and has both parents living.
Main Article Link:
http://www.jewishvirtuallibrary.org/jsource/Judaism/kaddish.html
Read More:
http://www.chabad.org/library/article_cdo/aid/282507/jewish/Soul-Talk.htm
Kaddish Trainer:
http://www.chabad.org/library/howto/trainer_cdo/aid/514194/jewish/Kaddish-Trainer.htm#!1/2/4/v2