Ctrl+Alt+F1-F12 switches to different virtual terminals on your computer. What is running on terminal 1-6 is
getty, which allows users to login to a CLI. Terminal 7 is probably running something like
tail -f /var/log/messages (it doesn't do that on my machine).
The configurations for these programs exists in
/etc/init/tty[n].conf on ubuntu. You can put any command here, but remember that they will run as the root user. The virtual terminals after 6 (or 7 in your case) are free so that the X server will be able to bind to one, otherwise the program running in the background of the virtual terminal would be able to interfere with your graphical session.
The reason for having these different virtual terminals is not actually debugging, but it is a historical relic from the time of timesharing systems, where several users would use the same mainframe from different terminals.