Android 6.0 Marshmallow introduces new Assist API. This API presents a new way for users to engage with apps. Users summon the assistant with a long-press on the Home button or by saying the keyphrase. In response to the long-press, the system opens a top-level window that displays contextually relevant actions for the current activity. These potential actions might include deep links to other apps on the device.
From this guide you’ll know how to use Assist API to improve the assistant user experience.
Link to the guide: Using the Assist API