Answer:
Sunni is the largest branch of Islam.
Shia believe Ali is the legitimate successor to Muhammad, practiced mainly in Iran.
Sunni believe the caliph Abu Bakr was the rightful successor to Muhammad.
Step-by-step explanation:
Sunni Islam is the main branch of this religion, consisting of approximately 85% of the world total of Muslim faithful. This current recognizes Abu Bakr, father-in-law of Muhammad, as the spiritual successor of the prophet. Its faithful have the Koran and Sunna as their sacred book, and it is the predominant religion in the entire Middle East with the exception of Iraq, Iran and Azerbaijan.
In contrast, Shiite Islamism is the second most important branch of Islam, with approximately 15% of the faithful. This branch is majority in countries such as Iran, Iraq and Azerbaijan, and recognizes Ali, Muhammad's cousin, as his successor.
Furthermore, it is generally the case that Sunnies are more orthodox, while Shiites are a much more disruptive current within the religion itself.