If you "Open from location" instead of "Save to Disk", does this mean the file is not really saved on your computer?

If email comes with a .txt document. I have the option of “open file from location” or “save to disk”. We all know what save to disk does.

But if I choose the first option, does this mean, that I’m only temporarily viewing the document and its not really saved?

And if it is saved, where would it be?