Add glossary of terms to documentation

[by22Jy]

Summary

Adds a glossary section to Click's documentation defining key terms used throughout the docs.

Changes

• Added docs/glossary.rst with definitions for 10 key terms
• Updated docs/index.rst to include the glossary in General Reference section

Terms Defined

• Argument: Positional parameter passed to a command
• Callback: Function invoked when a parameter is processed
• Command: Function decorated with @click.command() or @click.group()
• Command Line Interface (CLI): Text-based interface for program interaction
• Context: Object carrying state between commands
• Flag: Boolean option without a value
• Group: Command containing subcommands
• Multi-command: Command grouping multiple subcommands
• Option: Named parameter with dash prefix
• Parameter: General term for options and arguments

Closes #3077

Checklist

• Documentation builds correctly
• Follows existing documentation style
• Terms are clear and consistent with Click's usage

[nrschroeder]

This looks good ... the glossary seems like it will make the docs a lot clearer.

One thing I noticed while reading the issue is that it also mentioned terms like “terminal”, “command line application”, and “command line utility”. Since those show up in different places in the docs as well, it might be helpful to include them here too for completeness.

[by22Jy]

Hi @nrschroeder, thank you for the great suggestion! I've added the three additional terms you mentioned:

• Terminal: A text-based interface for interacting with the operating system
• Command Line Application: A Python program built with Click that provides a CLI
• Command Line Utility: A command line application designed to perform specific tasks

These terms will definitely help make the documentation more comprehensive. Let me know if you'd like any adjustments to the definitions!

[AndreasBackx]

Would love to primarily get some input from others here. I think this is great to have however, thank you!

[AndreasBackx]

Suggested change

	Multi-command
	A command that groups multiple subcommands together. Groups and
	multi-commands are similar concepts in Click.
	Multi-command
	Alias for Group, used to have a slightly different implementation.
	Planned for removal in 9.0.

[AndreasBackx]

I'm not too familiar with how glossaries work in Sphinx. But will "option" here link to the glossary for that word down below automatically or does that need to be done explicitly here and elsewhere in the code? I hope it's the latter.

[AndreasBackx]

Correct me if I'm wrong here. But I feel like "CLI" is common nomenclature for the application, regardless of what the true acronym stands for.

Suggested change

	Command Line Application
	A Python program built with Click that provides a command line interface.
	Command line applications use commands, options, and arguments to interact
	with users through the terminal.
	Command Line Interface (CLI)
	A text-based interface for interacting with a program through commands,
	options, and arguments. Click helps you build CLIs in Python.
	Command-line Application
	Application meant to be interacted with using a command-line interface.
	Often referred to as a CLI as well, even though it's not the true acronym.
	Command-line Interface (CLI)
	A text-based interface for interacting with a program through commands,
	options, and arguments. While CLI is its acronym, a CLI often refers to
	an application written for the command-line interface.

[AndreasBackx]

Suggested change

	Command Line Utility
	A command line application designed to perform a specific task or set of
	tasks. Command line utilities are often used for system administration,
	file manipulation, or development workflows.

Personally I'd remove this to avoid confusion.

[davidism]

Unfortunately gen AI, which we don't accept