Terminal and CLI

The terminal is the window; the shell is the program inside it that reads commands and runs them: bash on most Linux servers, zsh on macOS, PowerShell on Windows. A CLI (command-line interface) is any program built to be used this way, such as git, npm, docker or a cloud provider's own tool. Commands can be chained together and saved in scripts, which is why automation and CI are built on the command line.

Servers usually have no graphical interface at all, so managing one means connecting over SSH and working in the shell. Windows developers often add WSL to get a real Linux shell. Terminal apps such as Windows Terminal, iTerm2 and the one built into VS Code differ in comfort features, but the commands are the same.