Difference between Wajib, Mandub, Mustahab, and Sunnah

Q: What is the difference between Wajib, Mandub, Mustahab, and Sunnah?

A: All Praise is due to Allah Alone. Peace and blessings be upon Allah's Messenger, his family, and Companions. To proceed: These terms differ according to the following terminology: (i) One who performs a Wajib (obligatory) act is rewarded; however, if one does not perform such act, punishment is incurred. (ii) Mandub (commendable), Mustahab (desirable), and Sunnah (whatever is reported from the Prophet) are similar, if not synonymous. All of these terms refer to a category of acts that if one performs, one will be rewarded, but if one does not perform, one will not be punished.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.