Check out example codes for "check google api key". It will help you in understanding the concepts better.

Code Example 1

Google API Web Check: http://yougapi.com/tools/google-api-key-checker.php
Chrome extension API check: https://chrome.google.com/webstore/detail/google-maps-platform-api/mlikepnkghhlnkgeejmlkfeheihlehne/related 
"Note: Keep in mind that if you use the web check that we don't know what happens with the data"

Code Example 2

You also have to get a key
go to https://hospitable.live to see how it works
a[href^="http://maps.google.com/maps"]{display:none !important}
a[href^="https://maps.google.com/maps"]{display:none !important}

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