What is a shell in Linux?

A shell is a command-line interpreter that accepts user commands and passes them to the operating system for execution. It serves as an interface between the user and the kernel. Common shells include Bash (Bourne Again Shell — default on most Linux distros), sh (Bourne shell), zsh, fish, and ksh. The shell also provides scripting capabilities: variables, loops, conditionals, and functions. When you open a terminal, you are interacting with a shell process. You can check your current shell with echo $SHELL.