Screen went black [duplicate]

I'm new to Ubuntu..

I'm not sure what just happened, but the screen just went black with the text: Ubuntu 11.10 "my computer name" tty4

and I was asked to log on.

It happened when I closed Chrome (Alt+F4). This is the second time it has happened, and I cant make it go away :) Even if I log on. Only thing that works is to press Ctrl+Alt+Delete, which makes my PC restart.

Any idea what is causing this?

Looks like you accidentally switched to the text console, that does no harm at all as long as you know how to return to your desktop. Did you accidentally hit Ctrl+Alt+F4? In that case you can return to your desktop hitting Ctrl+Alt+F7.

There are usually 6 text consoles (F1 - F6) but most users aren't even aware of them. They're extremely useful for troubleshooting, but otherwise barely used these years. I think the main use is in servers with usually no GUI (graphical user interface) available.

The shortcut including the F7 key didn’t work for me in Ubuntu 18.04. Instead, Ctrl+Alt+F1 worked to get back.