NOTE: You need to go to Site Properties, and put the Google Places API KEY in the Default Value.

Autocomplete is a feature of the Places library in the Google Maps JavaScript API. You can use autocomplete to give your applications the type-ahead-search behavior of the Google Maps search field. When a user starts typing an address, autocomplete will fill in the rest.

Google Autocomplete adds a text input field to your web page, and monitors that field for character entries. As the user enters text, autocomplete returns place predictions in the form of a dropdown pick list. When the user selects a place from the list, information about the place is returned as a JSON string via the widget, and can be processed by your application as raw JSON or as a record.

For more info see here.