init the most essential program for UNIX systems. Started as first process generally with PID 1, when system boots up. Nothing to worry about it because it is already configured to work in any system.init starts other processes directly or indirectly.
e.g. init starts a separate instance of getty(responsible for logins) when asked.
getty reads the username and runs the login program, which reads the password if every thing is fine then it runs the shell.

‘init’ dies last
When the system is shut down, it is init that is in charge of killing all other processes, unmounting all
filesystems and stopping the processor.