Sallallahu Alayhi Wasallam is a salutation (meaning May Allah honor him and grant him peace) for the last and the most noble Prophet Muhammad Sallallahu Alayhi Wasallam.
Sallallahu Alayhi Wasallam is also called as the greetings for the Prophet Muhammad and a special Salam on his personality. The word of Allah i.e. the Holy Quran also comments on this philosophy and says: ‘Allah and His angels send Salawat (Translated as sending blessings) on the Prophet: O ye that believe! Send Salawat on him, and salute him with all respect.’
The Salawat of Allah and His angels on Prophet Muhammad is not comprehensible for human beings however as for our part of Salawat, there are different authentic Salawats and Duroods for the Prophet Muhammad, Sallallahu Alayhi Wasallam is the shortest Salawat for the Prophet peace be upon Him.
The Salawat is in no way return to the Prophet Muhammad Sallallahu Alayhi Wasallam efforts and struggle to save the men kind from hellfire. It is just a greeting from the men who understand the The Prophet Muhammad’s contribution to save humanity.