Sunnis and Shiites. They are just to Islamic schools that differ in minor issues. The outsiders are trying to feed up assumed differences and conflicts between Muslim groups to gain control on Muslim countries and on their resources. The two main groups are Sunnis and Shiites. Both groups agree upon basic Islam pillars, believe in same and only version of Quran, believe and follow the sunnah of same prophet (PBUH), pray to same direction (facing Kaba in Makkah or Mecca in Saudi Arabia, go to same places on pilgrimage (or Hajj), and adhere to same Islam morals and ritual worships. They only differed on some side issues that are not critical.
Sunni.
Muslims were divided into two groups
There are shia muslims and sunni muslims in islam.
Islam's two major sects are the Sunni Muslims and the Shia Muslims.
The Sunni Muslims form the largest group (about 85%) of the Muslims. There are many brnches of smaller groups like Shias, Wahabis, Ahl-i-Hadith etc.
How about the Christians and Muslims
The two largest minority groups in the US are Hispanics/Latinos and African Americans.
The two largest ethnic groups in Yugoslavia were the Serbs and the Croats.
Hinduism , Muslims
There are more than two groups of Muslims, but the dominant two sects of Islam (accounting for >99% of all Muslims) are the Sunnis and Shiites. To read about their differences, please see the Related Question below.
Sunnis and Shiites.
The two largest ethnic groups in the United States are white and black African American.