Many applications are designed to work inside a shell, but some of them are mimicking the shell's behavior. Graphical interfaces have a Terminal emulator that is designed for executing shells. These types of applications are called pseudo-teletypes (PTY). In order to be considered a PTY, an application needs to be capable of the following:

• Accepting input from the user 
• Sending input to the console and receiving the output
• Showing this output to the user

There are some examples already in the available Linux utilities, screen being the most notable. It is a pseudo-terminal application that allows the user to use multiple shells and control them. It can open and close new shells, and switch between all opened shells. It allows the user to name a session, so that, if it's killed for any unexpected reason, the user can resume the session.