It is a ritual that is designed to promote the bonds of Islamic brotherhood and sisterhood by showing that everyone is equal in the eyes of Allah.
The Hajj makes Muslims feel real importance of life here on earth, and the afterlife, by stripping away all markers of social status, wealth, and pride. In the Hajj all are truly equal.
The Hajjis or pilgrims wear simple white clothes called Ihram. During the Hajj the Pilgrims perform acts of worship and they renew their sense of purpose in the world.
Mecca is a place that is holy to all Muslims. It is so holy that no non-Muslim is allowed to enter.
For Muslims, the Hajj is the fifth and final pillar of Islam. It occurs in the month of Dhul Hijjah which is the twelfth month of the Islamic lunar calendar. It is the journey that every sane adult Muslim must undertake at least once in their lives if they can afford it and are physically able.