In Islam, there are two main sects: Sunni and Shi'a. Sunni Islam is the largest sect, although in some countries it is a minority. Sunnis have their historical roots in the majority group who followed Abu Bakr, an effective leader, as the successor of Muhammad, instead of his cousin and son-in-law Ali. The Sunnis are so named because they believe themselves to follow the sunnah or "custom" of the Prophet. Shi'a Muslims or Shi'ites are those Muslims who followed Ali, the closest relative of Muhammad, as Muhammad's successor. The following chart compares some basic facts about Shi'a and Sunni Islam.