ANSWER:

Sunnah and nafl have the same meaning which is what a person does, he will be rewarded for it and if he doesn’t do it, he won’t be sinful. 

In my country, Bangladesh, people are fighting saying Is Taraweeh sunnah or Nawfl.If Tahajjud sunnah or Nawfl.Some are saying tahajjud=tareweeh!please clarify

Taraweeh, Tahajjud and Qiyam-ul-Layl |