I keep hearing about these things known as
what are they
how can I access them
what do they do?
tty is one of those funky Unix commands that prints (or, displays) to standard output the name of the terminal connected to standard input.
These are commonly used as a way to get access to the computer to fix things, without actually logging into a possibly b0rked desktop.
Related: What is tty7 in the commandline?
By default Ubuntu has 7 tty's.
To access them, use this keyboard shortcut:
Ctrl + Alt + F1
To get back to your X session (the normal desktop),
Ctrl + Alt + F7