What is the `sensor` parameter for in the Google Places API?

Edit: The sensor parameter is no longer required, and will now be ignored if it's used.

The parameter doesn't impact the results. It's a parameter that Google is required to collect for Google's data providers who charge differently based on whether the request uses a sensor or not.

see Google docs

The Google Maps docs have been updated and as of June 2014 and the &sensor parameter is no longer required for JavaScript or Web Service API calls. The parameter will now be ignored if passed along with any request.

docs - https://developers.google.com/maps/documentation/javascript/tutorial