The continued conversation feature was announced at Google I/O as an optional setting, which lets the user have a natural back-and-forth conversation with the Assistant without repeating ‘Hey Google’ for each follow-up request. Starting today, the new feature has been rolled out as an update, and users, after updating the eligible device, can turn it on by going to Settings -- Preferences -- Continued Conversation and hitting the toggle.
With continued conversation turned on, you can ask the Assistant a question followed by any other command such as setting a reminder, or adding something to your shopping list, without having to say ‘Hey Google’ each time. You can say 'thank you' or 'stop' once you are done, or the conversation will end once the Assistant recognises that you are no longer talking to it.