This is a so called QgsLocator filter for the TomTom API search service, implemented as a QGIS plugin.
Read about writing one here:
http://www.qgis.nl/2018/05/16/english-coding-a-qgslocator-plugin/
This Locator Filter searches for names in the TomTom API search service:
see https://developer.tomtom.com/search-api/search-api-documentation-geocoding/geocode
You can install this 'Locator Filter' as a plugin by searching for it in the QGIS plugin manager in your QGIS desktop, search for 'TomTom':
http://plugins.qgis.org/plugins/tomtom_locator_filter/
Some more docs and api's:
http://api.qgis.org/api/master/html/classQgisInterface.html
http://python.qgis.org/api/core/Locator/QgsLocator.html
http://python.qgis.org/api/core/Locator/QgsLocatorFilter.html
You need to grab an API Key from TomTom here: https://developer.tomtom.com/user/register
This plugin is based on QGIS Nominatim Locator Filter Plugin: https://github.com/rduivenvoorde/nominatim_locator_filter