--output-document=file name)is not intended to mean simply "use the name file instead of the one in the URL"; rather, it is analogous to shell redirection:
wget -O file URL is intended to work like
wget -O - URL > file. The file will be truncated immediately, and all downloaded content will be written there. However, you can simply understand it as renaming the downloaded file.
wget -O vpsname.ico https://vpsname.com/favicon.ico # same way wget --output-document=vpsname.ico https://vpsname.com/favicon.ico
Well, when you execute this same command again, Wget will not add a number to the end of the file. Yes, the original file has been overwritten. You can run the command above as many times as you like and Wget will download the file and overwrite the existing one. If you run the command above without the
-O option, Wget will create a new file each time you run it.
o. You should use the capital "O" here.