Usually it's a good thing when a company wants to listen to its users, but in this case not so much. In the latest update for Windows 10, Microsoft has decided Cortana will be listening to you regardless of your settings. Furthermore, Cortana will only use Bing to search and open the results in Microsoft Edge, regardless of your browser and search preference settings.
Prior to now, there was an option to shut Cortana off and just use a basic textual search. In their wisdom, Microsoft has not only reactivated Cortana but also removed the option to turn it off. This means every desktop running Windows will be listening for key phrases, and possibly more. We already know Microsoft will send personal information in the clear back to their servers.
If, like me, you hate the idea of your PC listening to your every utterance, you can manually edit your registry to deactivate this feature (until Microsoft changes it again). The instructions are here: link