Pilgrimage is a journey undertaken for a religious motive. Although some pilgrims have wandered continuously with no fixed destination, pilgrims more commonly seek a specific place that has been sanctified by association with a divinity or other holy personage. The institution of pilgrimage is evident in all world religions.
Since the 2nd or 3rd century CE, Christians have traced the events of the Bible, including the life of Jesus Christ himself, through visits to the Holy Land. Mecca is revered by Muslims as the dwelling place of Adam after his expulsion from paradise and as the birthplace of Muhammad (570–632), the prophet of Islam.
The Christian New Testament does not specifically enjoin believers to go on pilgrimage, but sacred texts in other religious faiths do. A hajj (formal pilgrimage) to Mecca is one of the five Pillars of Islam. According to the Bible, immediately after he was given the Ten Commandments, the Hebrew prophet Moses received instructions on Mount Sinai that required the Jewish people to appear before the Lord three times a year.
Pilgrimage usually entails some separation (alone or in a group) from the everyday world of home, and pilgrims may mark their new identity by wearing special clothes or abstaining from physical comforts. Frequently, pilgrimages link sacred place with sacred time. The hajj always occurs on the 8th, 9th, and 10th days of the last month of the Muslim year. Historically, Jews would visit the temple of Jerusalem during three annual festivals, as prescribed in Deuteronomy.
Apart from involving movement across physical and cultural landscapes toward a sacred goal, pilgrimages frequently involve ritual movements at the site itself. Performing the Stations of the Cross, which reenact the events of Jesus’ Passion, is a frequent activity at Roman Catholic shrines. Muslims walk seven times around the Kaʿbah, or central cube-shaped shrine, at Mecca.A further common feature of pilgrimages is the availability of small souvenirs—relics, containers of holy water, icons, and so on—that allow the sacredness of a shrine to be transported back to the pilgrim’s home.
Reference: Britannica’s entry on pilgrimage