As a demonstration of the point made clear by the existing answers I would like to add an example.

#!/bin/sh 
sleep 50 

let’s save it as a.sh and make it executable

sudo chmod +x a.sh 

Let's run it in the background and stat the process.

./a.sh& 
[1] 11660 

On looking at the process details:

 ps -fp 11660 
UID        PID  PPID  C STIME TTY          TIME CMD 
sudipbh+ 11660 11330  0 15:30 pts/7    00:00:00 /bin/sh ./a.sh 

We can see that the content of the file is passed as an argument to the program /bin/sh.

In Bash scripting, this enables the script author to mention the exact interpreter to be used by the program and if it’s not found the user can take it as a cue to install the required interpreter.

The same idea would be extended to other interpreted languages like python.