A Muslim is a believer in the religion of Islam. If you're a devout Muslim, you observe the holiday of Ramadan by fasting during the day for a month.
Muslims believe that the word of God is written in the Qur'an, the Islamic holy book, and they follow the teachings of the prophet Muhammad. Most Muslims place a lot of importance on the idea of serving God through prayer and certain standards of purity, like not drinking alcohol or eating pork. In Arabic, the word Muslim means "one who submits," from the root word aslama, "he resigned."