I am a student and learning about operating systems, I was modifying a file using vi, when I accidentally did something (I don't remember what) that change the codification/encoding and now this is how I see everything.

![this](https://i.stack.imgur.com/XbJdV.jpg)

That screenshot is while using `vi`, but the problem is system wide. I tried searching but couldn't find anything. 

I can delete, everything and reinstall, as it is just a virtual machine but I'd rather learn what happened.