Shell in Unix is a user interface that is used by a user to access Unix services.
Generally a Unix Shell is a command line interface (CLI) in which users enter commands by typing or uploading a file.
We use a Shell to run different commands and programs on Unix operating system.
A Shell also has a command interpreter that can take our commands and send these to be executed by Unix operating system.
Some of the popular Shells on Unix are: Korn shell, BASH, C shell etc.