7 Quick reference

7.1 Terminology

📓 Term	📖 What It Means
Command line	The interface where you type and run text commands
Shell	The program that interprets your commands and runs them (e.g. `bash`, `zsh`)
Terminal	The user interface that displays the shell and lets you interact with it. Examples: Terminal (Mac), Git Bash (Windows)
Directory (Folder)	A container for files
Path	The location of a file or folder
Flag	Extra option for a command

📝 Command	️💬 Action
`pwd`	Show current directory (path)
`ls`	List files and folders
`ls -l`	List with detailed info
`cd foldername`	Change into a folder
`cd ..`	Move up one folder
`mkdir name`	Make a new folder
`touch name.txt`	Create a blank file
`cp old new`	Copy a file
`mv old new`	Move or rename a file
`rm file`	Delete a file
`rm -r folder`	Delete a folder and its contents
`Ctrl + C`	Cancel a running command
Tab	Autocomplete file/folder names

❌ Error	📖 What It Means	💡 Fix
`command not found`	You typed a command the shell doesn’t recognize	Check for typos or whether the tool is installed
`No such file or directory`	You’re trying to access a file/path that doesn’t exist	Use `ls` to explore and make sure the path is correct
`Permission denied`	You tried to do something you don’t have permission for	Use `sudo` (if appropriate), or check file permissions
`Is a directory`	You tried to treat a directory like a file	Double-check what kind of thing you’re trying to use
`Not a directory`	You tried to treat a file like a folder	Use `ls -l` to see what’s a file vs folder
`Syntax error`	You typed a command in a way the shell can’t parse	Review the correct syntax, especially quotes or flags
`Killed` or `Terminated`	The OS stopped a program (often for high memory/CPU usage)	Try a smaller task or check system limits
Getting stuck in VIM	You opened something in `vim` and can’t exit	Press `Esc`, then `:q!`, then `Enter` / `return` to quit