The correct answer to this open question is the following.
Hijra a turning point in Islam in that it was in the city of Medina where Muhammad realized that there were many people that accepted him as the messenger of God. People there decided to convert to Islam and follow its precepts.
Hijrah is the pilgrimage that the Prophet Muhammad did from Mecca to Medina in 622 CE when he was escaping persecution. This date is identified by Muslim people as the beginning of the Muslim period. Muslim people have to follow five important pillars of Islam that are the Shahada or the profession of faith, Salat or daily prayers, Zakat or sharing with the ones in need, Saum that is fasting during the period of Ramadan, and Hajj that is the pilgrimage to Mecca at least one time.