What is al-uḍḥiya (qurbānī)?
Al-Uḍḥiya refers to an animal sacrificed as a devotional act at a given time. More specifically, it refers to certain kinds of animals (cattle) that are slaughtered during the days of Eid al-Aḍḥā.
This sacrifice was prescribed during the second year after hijrah, along with zakāh and Eid prayers. It is affirmed by the Quran, hadith and consensus of all Muslims.

Allah Almighty says:

So pray to your Lord and sacrifice (2:108)

And we have designated the budn for you(cows, oxen, or camels driven to be offered as sacrifices by the pilgrims at the sanctuary of Makkah) from amongst the Symbols of Allah. (22:36)

ʿĀʾisha –Allah be pleased with her- narrates from the Prophet –peace upon him: The son of Adam does not do any action on the day of slaughtering (Eid al-Aḍḥā) more beloved to Allah than spilling of blood of slaughtered animals. Surely the sacrificed animals will come on the day of judgement with their horns, hooves and coats. Verily the blood reaches a position of divine acceptance before it reaches the ground, so perform these rites enthusiastically. (al-Ḥākim, Ibn Mājah, al-Tirmidhī)