The Sunni's and Shi'ites (please excuse the misplacement of the ' mark, if it is)
Besides different tribes its mainly extremest Islams killing Jews and any other religion that is not theirs.
i think there are no sects
There are three sects of Judaism: Orthodox, Conservative and Reform.
The Shia (Shiite) and Sunni
The most compelling social issues in Iraq are sectarian in nature involving intolerance of differing sects as well as issues pertaining to governance.
To differentiate the different sects.
The Kurds belong to many different sects, most notably being the Sunni sect as the majority. There is also a the Shia sect from among Kurds, most from the Shia sect live in Iran and Iraq.
Iraqi Christians celebrate Christmas unless their sect frowns on it, as many Christian sects do.
There has virtually never been a time in Jewish history where there were no differing sects of Judaism. Sects come about as the result of different interpretations of the Torah and Talmud.
There are no formal sects in Confucianism.
jainism
There is many Sects in Islam, there is also diffrent types of Sunnis with different beliefs, sub sects within.
In July 2006 estimate Iraqi population is above 27,000,000. The religious compisiton in Iraq is: Muslim 97% and Others 3% The Muslims here are divided in two sects: the Shia 60% and the Sunni 40%.