Eid al-Adha is the Feast of Sacrifice for Muslims, celebrated together with the pilgrimage to Mecca to be observed at least once in a lifetime.
The name "Adha" means sacrifice and is related to the sacrifice made by the prophet Abraham or Ibrahim.
The prophet Abraham/Ibrahim, as a faithful obedient to God was put to the test, sacrificing his son as an act of obedience. Abraham was stopped in time by the Archangel Gabriel because he had passed the test and the sacrifice was made to the ram, replacement animal.
The feast celebrates faith and total devotion to ALLAH (God) as Easter for Christians.