Goolge can be a very powerful tool in your OSINT toolkit. Google dorking or Google hacking is the art of using specially crafted Google queries to expose sensitive information on the Internet. Such a query is called a Google dork.
You may find all sorts of data and information, including exposed passwd files, lists with usernames, software versions, and so on.
If you find such an exposed web server, do NOT click on the links from the search results. Such an act may be considered illegal! Only do this if you have written permission from the target system's owner.
A good resource for finding Google dorks is the Google Hacking Database located at https://www.exploit-db.com/google-hacking-database.
You shouldn't enter any spaces between the advanced search operator and the query.
site: - restricts the search results to those only on the specified domain or site
inurl: - restricts results to pages containing the specified word in the URL
allinurl: - restricts results to pages containing all the specified words in the URL
intitle: - restricts results to pages containing the specified word in the title
allintitle: - restricts results to pages containing all the specified words in the title
inanchor: - restricts results to pages containing the specified word in the anchor text of links located on that page
allinanchor: - restricts results to pages containing all the specified terms in the anchor text of links located on that page
cache: - displays Google's cached version of the webpage instead of the current version
link: - searches for pages that contain links pointing to the specified site or page
related: - displays websites similar or related to the one specified
info: - finds information about a specific page
location: - finds location information about a specific query
filetype: - restricts results to the specified filetype