What is the Koran, and what role did Muhammad play in its creation?

The Koran or Quran is the holy book of the religion of Islam and one of the faiths 5 pillars of faith

Muhammad(PBUH) was for the majority of his life a simple Arabian man, until according to the Quran the angel Gabriel descended upon him one day to bestow the command of god upon him whilst he was meditating in a cave in the mountains of mecca, this commandment of god was that Muhammad(PBUH) was to relay gods command and messages to the people of Mecca and the Arabian peninsula, the Quran is the compilation of those messages into text