(CNN) -- Five things to know about Eid al-Adha:
1. Considered one of Islam's revered observances, the four-day religious holiday corresponds with the height of the Hajj -- the pilgrimage to Mecca in Saudi Arabia that annually draws 2 million Muslims.
2. Eid al-Adha commemorates when God appeared to Abraham -- known as Ibrahim to Muslims -- in a dream and asked him to sacrifice his son as an act of obedience. As Abraham was about to sacrifice his son, God stopped him and gave him a sheep to kill in place of his son. A version of the story also appears in the Torah and in the Bible's Old Testament.
3. Pronounced EED al-UHD-huh, the holiday begins Friday and ends Monday -- the last day of the Hajj. Eid al-Adha is also known as the Feast of Sacrifice or Greater Eid. It is the longer of two Eid holidays observed by Muslims. Eid al-Fitr -- or Little Eid -- follows the conclusion of the holy month of Ramadan.
4. During Eid al-Adha, many Muslim families sacrifice a sheep and share the meat with the poor. They also are required to donate to charities that benefit the poor. Muslims also routinely exchange presents during the holiday.
5. Eid Mubarak (pronounced EED muh-BAR-ack) and Eid Saeed are routine greetings used during the observance to offer best wishes.
CNN's Chelsea J. Carter and Hamdi Alkhshali contributed to this report.