* A shell is an interface/command line for the user. A shell provide an environment to user to execute commands and interact with kernel.
*Shell scripts consist of a set of commands to perform a task. All the commands execute sequentially. some tasks like file manipulation, program execution, user interaction, automation of tasks, etc can be done.
#!/bin/bash is a shebang line. It tells the Linux OS which interpreter to use to parse the rest of the file.
*Bash*sh
*ksh
*tsh
*fish
*zsh
VAR_NAME=value
VAR_NAME=$(hostname)
echo $VAR_NAME