What is a terminal emulator?

A terminal emulator is a GUI program that draws a fake text terminal in a window — the thing you actually open when you "open the terminal" on a desktop.

* The three loosely-used layers made concrete: the emulator is the window, the PTY is the device it allocates, the shell is what runs inside it. *

The old physical terminals are gone, but tons of software still expects to talk to one. A terminal emulator bridges that gap: it pretends to be a hardware terminal so a shell running inside it behaves exactly as it would on a real console — same Ctrl+C, same line editing — except now it's a resizable, copy-pasteable window on your desktop.

Under the hood it does three things: open a window, allocate a pseudo-terminal (PTY) from the kernel, and start a shell (e.g. bash) attached to that PTY. That PTY is exactly why your terminal session shows up as /dev/pts/0 rather than a real tty.

Practical wins over a raw text console: multiple tabs/windows at once, mouse copy-paste, scrollback, and custom fonts/colours — all while the graphical desktop keeps running alongside.

Gotcha: "terminal," "shell," and "terminal emulator" get used loosely but are three layers: the terminal emulator is the window, the terminal (PTY) is the device it provides, and the shell (bash) is the program running inside that interprets your commands.

Go deeper:

• pty(7) — Linux manual page — the PTY a terminal emulator allocates so a shell behaves as if on real terminal hardware.