Forum Moderators: phranque
It wasn't me, so just a guess. Maybe this person was looking for files with extensions like '.doc' , '.pdf' and decided to exclude '.htm', '.html' and '.php' files. The 'site:us' restrict the search to domains with a 'us' ccTLD (country code Top-Level Domain). A lot of '.com' domains are not in the US or US related. So this person might have thought that adding 'site:us' would help to get info from an American page.