Aḍḥā means sacrifice. 

Eid al-ʿAḍḥā occurs on 10th day of the Islamic month of Dhul Hijjah during the annual Hajj Pilgrimage. It celebrates the readiness of Prophet Ibrahim (‘a) to sacrifice his son Ismail (‘a) in obedience to the command of Allah

Before Prophet Ibrahim (‘a) could sacrifice his young son Ismail (‘a), Allah sent a lamb instead for the sacrifice. 

Muslims believe this event occurred in Mina (a desert outside Mecca), and so Hajj pilgrims spend the morning of Eid al-ʿAḍḥā in Mina preparing and offering their own animal sacrifice as a part of the rites of Hajj.

Muslims around the world traditionally celebrate Eid al-ʿAḍḥā by sacrificing an animal; most often, sheep and goats. The meat is usually distributed as charity. 

The Muslims – those who are performing the Hajj as well as those who are not on the Hajj, will also perform the Eid prayers, exchange gifts and sweets, and visit extended family. 

Fasting is forbidden on this day.