PTY (pseudo-terminal)

A software-defined terminal pair that emulates physical hardware to bridge interactive programs with system processes.

PTYs function as bidirectional communication channels consisting of a master-slave pair (typically /dev/ptmx and /dev/pts/N). The master side mimics the hardware controller, while the slave side provides a standard terminal interface for shells like Bash or Zsh. This abstraction allows tools like SSH, Tmux, and Expect to trick applications into believing they are connected to a physical serial line or VGA console. By intercepting signals and line-discipline logic, PTYs enable remote command execution and terminal multiplexing across modern networks.

https://man7.org/linux/man-pages/man7/pty.7.html