It is a shell around the O.S kernel and could be used to perform a lot of tasks using Command Line Interface (CLI).
There are lot of shell available and my favorite is iTerm2 on macOS. It has host of different functionalities embedded in it and supports various environments.
You could create a .sh file for making all of these commands and saving it in the file to execute sequentially in order.
Sometimes we need to provide some execution permissions for the script or else it would be dangerous for every other script to run just by double clicking it.
chmod x script_nameAnd to run the shell script on some of default shells like bash or zsh you can just type
sh script_name
#or
> . script_name.sh