The Loqate address lookup widget is a PAF Widget (Postcode Address File) that uses the api service from Loqate.com [formerly Addressy, PostcodeAnywhere and Matchcode360].
Loqate offers extremely powerful search features which require an extremely capable search widget.
Loqate allows you to search not just on a post code but on any part of an address in full or partial.
Depending on your search definition the search which uses “find” will return a list of matched address. If your selected option has another level of detail (i.e. selecting a flat block) a second narrower search list will be offered in the same dropdown after selection.