What is a Google Dork?
Some Google Hacking...
Google Dork is an advanced Google search query using special commands such as allinurl, allintitle, etc to leverage Google to find public information. Is also a good way to perform passive reconnaissance, see the section below:
Offensive Security has the major Google Dork database called GHDB, have a look here: https://www.exploit-db.com/google-hacking-database