Applications
The role of the terminal emulator process is to interact with the user; to feed text input to the master pseudo-device for use by the shell (which is connected to the slave pseudo-device) and to read text output from the master pseudo-device and show it to the user. The terminal emulator process must also handle terminal control commands, e.g., for resizing the screen. Widely used terminal emulator programs include xterm, GNOME Terminal and Mac OS X Terminal. Remote login handlers such as ssh and telnet servers play the same role but communicate with a remote user instead of a local one. Different again are programs such as expect.
Screen and Tmux are used to add a session context to a pseudo terminal, making for a much more robust and versatile solution. For example, it provides terminal persistence allowing to disconnect from one computer and connect later on from another computer on the net.
Read more about this topic: Pseudo Terminal