1. What is a Shell?

• A shell is a program that takes what you type (commands) and tells the operating system to run them.
• It’s called a shell because it’s the outer layer you interact with (not the OS kernel directly).
• Examples of shells:
  • bash (Bourne Again Shell, default in most Linux).
  • zsh (popular alternative, default on macOS now).
  • fish, csh, etc.

👉 Think of the shell as the “language interpreter” for your commands.

2. What is a Terminal?

• A terminal is the program that shows you the shell.
• Historically: a physical terminal (keyboard + screen connected to a mainframe).
• Today: software like gnome-terminal, iTerm2, Windows Terminal.

👉 Terminal = the window/program you see.

👉 Shell = the thing running inside the terminal.

Analogy:

• Terminal = the car dashboard.
• Shell = the steering wheel you use to give commands.
• Kernel/OS = the engine that makes things happen.

3. What is Bash?

• bash = “Bourne Again SHell.”
• It’s the most common shell in Linux and Raspberry Pi OS.