Islam was founded by Muhammad (570-632). The word 'Islam' means 'surrender' (to the One God, who is Allah). It was founded when Muhammad was 40 years old, as he began to receive the words from God after a long meditation. The Islamic movement began as a continuation of (or even restoration to) the Jewish and Christian religions.
Two important places for Islam: Mecca and Medina. Mecca is the birthplace for Muhammad, and Medina is the place he retreated when he left Mecca due to oppositions during the early years. This migration is also marked as a turning point in his life and in Islam, and the event is coined 'Hijra'.
Muhammad's involvement in Islam lasted roughly 22 years and usually divided into two periods: the first 12 years in Mecca, and the last 10 years in Medina. However, he did return to Mecca by conquering it before his death. In his life time he united the tribes in Arabia into one religion entity.
After his death, the Islam movement eventually separated into two main branches: the Sunni and the Shi'a. Sunni is formed by one of Mohammad's wives, Aisha, who is called 'the favorite wife of Mohammed' by her followers. Shi'a is formed by one of Mohammad's daughters, Fatimah, who is regarded as 'the only daughter' of Mohammed. Historians believe that Mohammed had four daughters and two sons by his first wife alone, but half of them died before he. Mohammed married multiple times after his first wife died.