You probably already happened, as a result of any command, to have completely unreadable characters in your terminal, forcing you to close it and open another.
Know that there is a trick to get it. This includes using the reset command which resets a shell to its original state.
Example of use:
$ cat /bin/cat
I advise you, at this moment, to look only at your keyboard and type the reset command and hit enter:
Your terminal will be usable again.