The two branches in Islam are Sunni and Shi’a. Sunni and Shi’a ideologies differ from each other, but only to some extent. You should know that both sects believe in same God, Allah only and in same Holy Book, i.e. Al-Quran. Sunni followers believe that Muhammad had not appointed a specific successor after his death. The Shi’a followers believe that Muhammad did choose a successor, Ali ibn Abi Talib.