Pseudoterminals (also spelled “pseudotty” or “PTY”) are pseudo-devices used with ttys whose emulators run in userspace. Use the [tty] tag for broad (text terminal)-related questions, and the [console] tag for terminal devices pertaining to the system console.
A pseudoterminal (also spelled “pseudotty” or “PTY”) is a pair of character pseudo-devices.
One of which, the slave, provides access to (emulated) text terminal for programs (console applications) and can have attached processes. Respective special files lie in /dev/pts/ (in modern Unix98-compliant OSes) or have /dev/tty[p-za-e][0-9a-f] names for compatibility with older software.
Second, the master, is an endpoint for the terminal emulator that runs in userspace. Respective special files is either one /dev/ptmx multiplexer (in modern Unix98-compliant OSes) or have /dev/pty[p-za-e][0-9a-f] names for compatibility with older software.
