Muslims pray toward the Qiblah of Islam to commemorate the prophet Muhammad's journey from Medina to Mecca in 622 C.E. Since 622 C.E., the Qiblah of Islam has remained the direction from anywhere one is in the world that points toward the city of Mecca in modern-day Saudi Arabia. Prior to 622 C.E., Muslims prayed not in the direction of Mecca, but toward the sacred al-Aqsa mosque in Jerusalem.
While many roughly define the Qiblah of Islam as the direction that points toward Mecca, it is really the direction that points toward the Kaaba. The Kaaba is a black structure located in Mecca that contains several sacred artifacts. The structure is among the holiest sites in the entire Islamic world, and it is the final destination of the Hajj, the sacred pilgrimage that all Muslims must make at least once during their lifetimes if they are financially able.
Most modern mosques and Muslim prayer rooms contain a special structure called the mihrab. The mihrab is a small niche that indicates the Qiblah and toward which all Muslims pray at the appropriate times. Because the wall that contains the mihrab indicates the Qiblah of Islam, it is often called the "Qiblah wall" and is sometimes confused with the mihrab itself.