Android 9 Pie is out today and it comes with Google's first ever gesture-based navigation system. That, however, is opt-in at the moment, for devices that are getting updated to Pie. You can enable it if you want, otherwise you're still able to use the traditional navigation with three software buttons - Back, Home, and Recents. This situation will not remain the same going forward. For Google devices launching in the future, including the Pixel 3 and Pixel 3 XL which should be made official at an event on October 4, the traditional buttons will be gone. Thus, the one and only...
Source: https://www.gsmarena.com/pixel_3_will_only_have_gesturebased_navigation_no_traditional_software_buttons-news-32621.php
