Witr And Tahjjud
Walekum as Salam 1) Witr and Tahajjud is the same prayer. They are not two individual prayers. See the video below at around 2:00. It’s called Qiyam ul Lail. There’s many videos of Ghamidi Sir explaining them. 2) Wajib is a term used by Hanfi school of thought. The video explains that as well from the start. Ibadat can be mandatory or voluntary. Witr or Tahajjud is not mandatory. https://youtu.be/iBpPA2fl8UA?t=116
For further details , please refer to the videos shared in the following thread : Discussion 65419
1 ) Niyat kai liya dil ka irada hona chaiyai, alfaz kehna zaroori nhi. Tafseel kai liya neechay dii gae video mulahiza karain: 2 ) Dua-e-qanoot tahajjud/witr ka lazmi juz nhi hai balaky iktiyari amal hai. https://youtu.be/BbXzx6DQPXc