Eid Al-Adhha translates to 'The Celebration of the Sacrifice'. The word Eid means celebration or festival. The word Adhha comes from the word dhahiyyah (noun) which means slaughter or sacrifice (or victim).
Eid Al-Adhha is one of the two Eids (days of celebration in the Islamic calendar). The other Eid is Eid al-Fitr and happens at the end of the holy month of fasting, Ramadhan. Eid al-Adhha occurs on the tenth day of the last month of the Islamic calendar (Dhul-Hijjah).

Eid al-Adhha is celebrated to mark a significant historical event relating to Prophet Abraham (PBUH) when he was tested by his Lord who commanded him to slaughter his only son Ismaeel (Ishmael) (PBUH) and when he was just about to make the cut, God sent down a ram for him to slaughter instead. Abraham's faith had been tested and he had passed the test. This Eid is celebrated remembering this event and as part of the rites of pilgrimage (the Hajj), the people who do the pilgrimage must slaughter/pay-to-slaughter an animal likewise and distribute the meat amongst their family, other pilgrims, relatives, friends and the poor.