Short answers, pulled from the story.
As of 2020, according to Pew estimates, there are roughly 2 billion Muslims, comprising about 25.6 percent of the world's total population. Islam is the fastest-growing religion in the world, driven by a younger average age and a fertility rate of 3.1 children per Muslim woman compared to the global average of 2.5.
Muslim is the active participle of the same Arabic verb root as Islam, the triliteral Š-L-M, meaning to be whole or intact. The Muslim philologist Ibn al-Anbari defined a Muslim as a person who has dedicated worship exclusively to God. Quranic studies scholar Mohsen Goudarzi has argued the Quran uses the word muslim to mean monotheist in a broad sense.
Sunni Muslims make up 87-90 percent of the global Muslim population, while Shia Muslims account for 10-13 percent. One defining difference is the Shahada: in Shia Islam, the declaration of faith includes a third phrase concerning Ali, the first Shia Imam, translating as "Ali is the wali of God", which Sunni Islam does not include.
Indonesia is the most populous Muslim-majority country, home to approximately 12.7 percent of the world's Muslims. Pakistan ranks second with 11 percent, followed by Bangladesh at 9.2 percent. South Asia as a whole accounts for 31 percent of the global Muslim population, the largest share of any region.
Many Muslims in English-speaking countries objected to the spelling Moslem because its "s" was often pronounced with a z sound, associating it with the Arabic triliteral ẓ-l-m, which carries negative meanings including the Arabic word for "the oppressor". The Associated Press instructed US news outlets to switch to Muslim in 1991, and the Daily Mail, the last major UK newspaper using Moslem, switched to Muslim in 2004.
The Five Pillars of Islam are the declaration of faith (shahada), daily prayers (salah), almsgiving (zakat), fasting during the month of Ramadan (sawm), and the pilgrimage to Makkah (hajj) at least once in a lifetime. To formally become a Muslim, a person must recite the Shahada in front of Muslim witnesses.