You can use the returning & new viewers metric to plan content strategy for your channel. For example, you can build loyalty by creating consistent content or you can experiment with new topics to attract new viewers.
Why don’t I see any “total” data for returning viewers when I select different dates?
What does it mean if my channel gets most of its views from new viewers?
What does it mean if my channel gets most of its views from Returning viewers?
Why are my returning viewers less than my subscriber count?
Does YouTube’s recommendation system optimize for returning viewers?
See an example
Check out the following video from the YouTube Creators channel to learn more about returning & new viewers data.