Islam is a monotheistic and Abrahamic religion articulated by the Qur'an, a text considered by its adherents to be the verbatim word of God (Arabic: الله Allāh) and by the teachings and normative example (called the Sunnah and composed of Hadith) of Muhammad, considered by them to be the last prophet of God. An adherent of Islam is called a Muslim.
Muslims believe that God is one and incomparable and the purpose of existence is to love and serve God. Muslims also believe that Islam is the complete and universal version of a primordial faith that was revealed at many times and places before, including through Abraham, Moses and Jesus, whom they consider prophets. They maintain that previous messages and revelations have been partially changed or corrupted over time, but consider the Qur'an to be both the unaltered and the final revelation of God. Religious concepts and practices include the five pillars of Islam, which are basic concepts and obligatory acts of worship, and following Islamic law, which touches on virtually every aspect of life and society, providing guidance on multifarious topics from banking and welfare, to warfare and the environment.
The majority of Muslims are Sunni, being 75–90% of all Muslims. The second largest sect, Shia, makes up 10–20%. The most populous Muslim-majority country is Indonesia home to 12.7% of the world's Muslims followed by Pakistan (11.0%), Bangladesh (9.2%), and Egypt (4.9%). Sizable minorities are also found in India, China, Russia, and parts of Europe. With about 1.6 to 1.7 billion followers or 22 to 24% of earth's population, Islam is the second-largest and one of the fastest-growing religions in the world.
Estimated Followers: 1.9 billion
Sources:
https://en.wikipedia.org/wiki/Muslim_world