There are 1.6 billion people worldwide that are classified as Muslims, according to the Population Reference Bureau. Adherents of Islam are expected to practice a set of core principles, known as the Five Pillars of Islam. They form the foundation of the teachings in the Quran, or Muslims' holy book.

Pillar One: Faith

The Koran and prayer beads

The first central tenet of Islam is the “Shahada” or declaration of faith. Muslims believe there is only one God, whom they call Allah -- meaning the God in Arabic -- and Mohammed is the prophet of Allah. A Muslim individual’s purpose in life is to obey Allah using Mohammed’s teachings to guide them.

Pillar Two: Prayer

Baghdad Ten Years After Invasion

Muslims must also practice “Salat” or ritual prayers. These must be performed five times throughout the day; at sunrise, midday, in the late afternoon, at sundown, and in the evening. Practitioners may pray anywhere, but are encouraged to pray in mosques with a group of believers. The Salat incorporates verses from the Quran spoken in Arabic. Believers may also offer additional personal prayers in their native languages and at any location and time of day. The prayers are offered while facing the direction of Makkah (Mecca) the holiest city of Islam.

Pillar Three: Charity

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Muslims believe that all things belong to God. Therefore, each Muslim must set aside a portion of his annual income to help the needy in his community. This principle is known as “Zakat” and must include at least 2.5 percent of an individual’s net capital. Zakat also includes a charitable attitude, showing kindness toward others, doing good works, and avoiding doing evil deeds.

Pillar Four: Fasting

Israeli Arabs Celebrate Islamic Eid al-Fitr Feast

During the month of Ramadan, Muslims engage in ritual fasting known as “Sawm.” During the time of fast, Muslims eat and drink nothing from daybreak to sundown. At sunset, the fast is broken with a meal known as “iftar.” Following the meal, an extra worship session called “tarawih” is observed in addition to the regular evening prayers. After Ramadan, Muslims celebrate the end of the fast with a three day feast known as “Eid Al-Fitr” in Arabic. Through fasting, believers seek a closer relationship with God and establish a sense of self-control. Women who are pregnant or nursing, sick individuals or the infirm are not expected to fast at this time. They are expected to feed a needy person instead and make up the fasting at a later time.

Pillar Five: Pilgrimage

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At some point in his life, every Muslim is expected to make a trip to the city of Makkah (Mecca), in modern day Saudi Arabia. This pilgrimage is called the “Hajj,” and is the highlight of any Muslim’s spiritual journey. The Hajj occurs annually during the twelfth month of the Islamic calendar. At this time, Muslims from all over the world gather in Makkah to follow in the footsteps of the prophet Mohammed. The pilgrims wear very simple clothing to symbolize the equality of all believers. The Hajj allows Muslims the opportunity to meet and worship with adherents from all over the globe.