Answer:
The number of different players who started a session on a given day. The Unity Analytics system anchors its days on Coordinated Universal Time (UTC), so the DAU figure counts players between 0:00 UTC and 24:00 UTC, no matter which timezone they are located in. A new session is counted when a player launches your game or brings a suspended game to the foreground after 30 minutes of inactivity.
DAU includes both new and returning players.
DAU includes both new and returning players.