what is bin/bash

It is also called as sh-bang, hashbang, poundbang or hash-pling. In Unix-like Operating Systems when a script starting with a she-bang(#!) is executed as a program, the program loader parses the rest of the script’s initial line as a interpreter-directive. In simple words, the she-bang at the head of the script tells the system that this file is a set of commands to be fed to the command interpreter indicated.