pseudo-tty
Berkeley Unix networking device which appears to an application program as an ordinary terminal but which is in fact connected via the network to a process running on a different host or a windowing system. Pseudo-ttys have a slave half and a control half. The slave tty (/dev/ttyp*) is the device that user programs use and the control tty (/dev/ptyp*) is used by daemons to talk to the net.