Is offering a sacrifice on Eid ul Adha required?

I just got into a discussion with someone about this. They told me: Eid ul Adha is soennah Moekkadah, which means it's not mandatory, but recommended. However, they also sendإِنَّا أَعْطَيْنَاكَ الْكَوْثَرَ .1 فَصَلِّ لِرَبِّكَ وَانْحَرْ .2 إِنَّ شَانِئَكَ هُوَ الْأَبْتَرُ .3 1. which urges to me that it is mandatory. Some also say that a donation towards a good cause, such as a poor family is also ok. So what is it? Is it mandatory, or are donations accepted as well?