Short answers, pulled from the story.
Muhammad received the first verses of the Quran in the year 610 during the Night of Power on the mountain Jabal al-Nour near Mecca. This event occurred when the archangel Gabriel delivered the text to him while he was in a cave seeking silence.
The Hijra was the emigration of Muhammad and his followers from Mecca to the city of Yathrib, which became Medina, after twelve years of persecution. This event marked the birth of the first Islamic state and the establishment of the Constitution of Medina. The migration occurred in the year 622 and united the community against external threats.
The first four Rightly Guided Caliphs were Abu Bakr, Umar, Uthman ibn al-Affan, and Ali ibn Abi Talib. Sunnis believe the community chose the first three caliphs as the rightful leaders, while Shias argue that Muhammad explicitly designated Ali as his successor at Ghadir Khumm. Ali was assassinated by a Kharijite, and his son Husayn was martyred at the Battle of Karbala in 680.
The University of Al Karaouine was founded in 859 during the Islamic Golden Age. It stands today as the world's oldest degree-granting university and was part of a flourishing period of science, medicine, and philosophy under the Abbasid Caliphate.
The Ottoman Caliphate was abolished in 1924 after the Ottoman Empire dissolved following World War I. Selim I had claimed the title of Caliph in 1517 when he became the ruler of Mecca and Medina, but the position ceased to exist in the 20th century.
As of 2020, about 2 billion people, or 25.6% of the global population, identify as Muslim. The majority of these Muslims live in Asia, particularly in Indonesia, Pakistan, India, and Bangladesh.