What is meant by the Udhiyah (sacrifice)? And is it obligatory or Sunnah?

The Udhiyah (sacrifice) is what is slaughtered from the Bahimat Al-An'am (grazing livestock) during the days of Eid al-Adha as an act of drawing closer to Allah. It is one of the rituals of Islam legislated by the Qur'an, Sunnah, and the consensus of Muslims. Evidence for its legislation includes Allah's saying: ﴿فَصَلِّ لِرَبِّكَ وَانْحَرْ﴾ (So pray to your Lord and sacrifice), and His saying: ﴿قُلْ إِنَّ صَلاَتِى وَنُسُكِى وَمَحْيَاىَ وَمَمَاتِى للَّهِ رَبِّ الْعَـلَمِينَ﴾ (Say, "Indeed, my prayer, my rites of sacrifice, my living and my dying are for Allah, Lord of the worlds"), and His saying: ﴿وَلِكُلِّ أُمَّةٍ جَعَلْنَا مَنسَكًا لِّيَذْكُرُواْ اسْمَ اللَّهِ عَلَى مَا رَزَقَهُمْ مِّن بَهِيمَةِ الاَنْعَـامِ﴾ (And for every nation We have appointed a ritual sacrifice that they may mention the name of Allah over what He has provided for them of grazing livestock). From the Sunnah, the Prophet (peace be upon him) sacrificed two rams, and he resided in Madinah for ten years performing sacrifices. He said: "Whoever slaughters after the prayer has completed his ritual and followed the Sunnah of the Muslims." Scholars have differed regarding its obligation. The majority are of the opinion that it is a confirmed Sunnah, while others consider it obligatory. Sheikh Ibn 'Uthaymeen chose the opinion that it is a confirmed Sunnah for those who are able to afford it.