In Ubuntu, there are 6 virtual consoles, which can be accessed by pressing Ctrl +Alt + F1 - F6, and F7, to exit.
What are the differences between these virtual consoles? Do they run different things, such as the GUI? Can I use these consoles?
Maybe I am not experienced enough but I didn't find any difference among tty1 to tty6. However, sometimes I see system messages appear in tty1 after I boot my system.
By the way, Ctrl + Alt + F7 doesn't
I believe it stems from the desire to have and switch between multiple foreground applications/logins running at the same time. Since unix and linux were always designed to be a multi-user and multi-tasking environment from the beginning, before GUI or networking was invented, this was one method used and it is kept because it can be handy sometimes.
A bit more: number 1 is the 1st one and some distro's default to sending system messages to just that one.
Well OK there is a little difference, typically these days the higher numbers are for GUI, and lower numbers for text based interface. Though many distro's use 7-12 for GUIs and 1-6 for text interfaces, not all are like this, some have 1-4 and 5-8 for text/gui and do not assume you have keys F9-F12 as some old keyboards didn't.