The division between Sunni and Shia Muslims originated after the death of the Prophet Muhammad in 632 CE and arose from a disagreement over
who should succeed him as the leader of the Muslim community.
Sunni Muslims believed that the successor, or caliph, should be chosen through a consensus of the Muslim community, while Shia Muslims believed that the caliph should be a direct descendant of the Prophet Muhammad. The Shia believed that leadership should remain within the Prophet's family, starting with his cousin and son-in-law, Ali ibn Abi Talib, while the Sunni believed that leadership should be based on merit and piety.
This disagreement led to a split in the Muslim community, with the Sunnis following the leadership of the first four caliphs after the Prophet Muhammad, known as the "Rightly Guided Caliphs," and the Shia following the leadership of Ali and his descendants, who they believe were the rightful leaders of the Muslim community.
Over the centuries, this division between Sunni and Shia Muslims has deepened, with differences in theology, religious practices, and political beliefs. Despite these differences, both Sunni and Shia Muslims share many core beliefs and practices and consider each other to be part of the larger Muslim community.