The complexity of Islam. Not a unified religion but a divided religion into various factions, sects and cults.
There are 4 types of Muslims and groups.
1. Accept Quran, Hadith and Sunnah.
2. Quran and Sunnah only.
3. Quran only.
4. Quran and Hadith only.
Further divided up into:
4. Bahai Movement
6. Wahhabism (part of Sunnah and early Hadith)
7. Lahore Ahmadiyya Movement
8. Kharijite Islam
10. Messiah Foundation International
11. Nation of Islam
13. Five Percenters
14. Idara Tolu-e-Islam
15. Various terrorists organisations predominately from Wahhabism or Sunnah only groups.
Islam is not a monolithic faith. Muslims may believe it is united but this is far from reality with many stark differences. People will come across Quran only and Sunnah only groups. Whereas the majority believe in the Quran, Hadith and Sunnah of the Prophet. Extreme versions of Islam are taught in some groups even advancing terrorism. Be cautious of any group advancing terrorism and do not lend them your support.
The complexity of Islam is greater than what the average person believes or thinks. This accounts for the wide various interpretations of Islamic groups.