Terminal and Command-line
----------------------------------

.. admonition:: Overview
   :class: Overview

    * **Time:** 15 min

    #. Learn how to use SSH for secure remote access.
    #. Understand the basics of SSH keys for authentication.


Terminal
^^^^^^^^^^^^

A terminal is a text-based interface that lets users interact with the operating system by typing commands.

.. list-table:: Terminal Interfaces Across OS
   :header-rows: 1

   * - OS
     - Terminal App
     - Default Shell
   * - Linux
     - gnome-terminal, xterm, etc.
     - Bash / Zsh / Fish
   * - macOS
     - Terminal
     - Zsh (or Bash)
   * - Windows
     - Command Prompt / PowerShell / Windows Terminal
     - cmd / PowerShell / Bash (via WSL)

Shell
^^^^^^^^^^^^

A shell is a program that runs inside the terminal. It takes your commands, interprets them, and executes them.


.. list-table:: Common Shells
   :header-rows: 1

   * - Shell
     - Description
   * - Bash
     - Bourne Again SHell, widely used in Linux and macOS.
   * - Zsh
     - Z Shell, an extended version of Bash with additional features.
   * - Fish
     - Friendly Interactive SHell, known for its user-friendly features.
   * - PowerShell
     - A task automation and configuration management framework from Microsoft.

.. admonition:: Explanation
   :class: attention
   
    * **What it is**: A terminal is a program that displays a text-based interface to the user.
    * **What it does**: It allows you to type commands and see their output, enabling interaction with the operating system.
    * **Analogy**: Like a TV screen where you can see the content, but it doesn't process the information itself.


.. admonition:: Explanation
   :class: attention

    * **What it is**: A shell is a program that interprets the commands you type in the terminal.
    * **What it does**: It processes your commands, executes them, and returns the results to the terminal.
    * **Analogy**:  Like the set-top box behind the screen—it does the actual processing.


.. admonition:: Key Points
   :class: hint
   
    #. A terminal is a text-based interface for interacting with the operating system.
    #. A shell is a program that interprets and executes commands typed in the terminal.
    #. Common shells include Bash, Zsh, Fish, and PowerShell, each with unique features and capabilities.