It will be automatically installed in compatible Android phones in the coming weeks. Your phone should be running on Android 6.0 Marshmallow or Android 7.0 Nougat and has the Google Play Services properly installed.
Google Assistant promises a more conversational and personal approach to virtual assistants. It leverages the power of Artificial Intelligence or AI to achieve this.
It already comes with the Google Pixel smartphones, Android Wear and Google Home. New smartphones such as the LG G6 also has the Google Assistant pre-installed.