Glossary
Terminal
The window that displays a shell session.
A terminal (or terminal emulator) is the application that draws the black window, captures your keystrokes and renders text output. It is not the shell — it is the screen and keyboard the shell talks through. GNOME Terminal, iTerm2, Windows Terminal and Alacritty are terminals; bash and zsh are shells running inside them.
The distinction matters in practice: colors, fonts, tabs, scrollback and copy-paste are terminal features, while aliases, history and prompt behavior belong to the shell. When something looks wrong, knowing which of the two owns the behavior halves the search.
See it in practice
$ ttyPrints the terminal device your shell is attached to, e.g. /dev/pts/0. Inside a cron job or a pipe there is none — and programs behave differently when they notice.
Where you'll meet it
The program that reads your commands and runs them.
TTYThe terminal device a process is attached to — or is not.
stdout (standard output)Stream 1 — where a program writes its normal results.