Virtual Consoles enable multi-user logins on a single machine. For example, you can login with your account and also as a root.

 

By default, most Linux versions provide virtual consoles with these keys.

Ctrl + Alt + F1 – F6: Virtual Consoles

Ctl + Alt + F7: A console where X server is running.

 

X

• is an application that manages one or more graphical displays and input devices(mouse, keyboard, etc.)
• works as a server.

You have probably heard about X11, X server, or X window.

All of these mean the same, and X11 just means eleventh version of X.

 

You can use a command ‘w’ which shows a list of currently logged-in users. 

tty represents regular terminal.

pts represents pseudo terminal slave(e.g. ssh connection).