According to Wikipedia:
In computing, a hidden folder (sometimes hidden directory) or hidden file is a folder or file which filesystem utilities do not display by default when showing a directory listing.
ls command, of course, is a directory listing. The
-a option “do not ignore entries starting with .” (
ls man page)
So, yes the file is invisible, or hidden. But in the terminal, you are requesting to see all, including invisible or hidden, files.