What happens when you open a .docx document that is written in a font not available on your computer?

How can you find the name of original font?

I guess writer select automatically an other font. I tried to open a document written in Japanese. Writer shows the fond Droid Sans, and all the characters except number and Roman letters appear as squares. After changing to Droid Sans Japanese a few boxes are still left. I guess I have to install the original font on my computer, but I do not know the name of the font.