Pseudoterminal (pseudotty or PTY)

In Unix-like systems, a pseudoterminal is a pair of pseudo-device endpoints (files) which establish asynchronous, bidirectional communication (IPC) channel (with two ports) between two or more processes.

In the pair master controls slave (like remote login/terminal) and slave acts like serial port for shell programs, enabling two-way communication

To control master through provided means used special terminal emulator applications, like foot.