Comment by yellowbkpk

For it to be really useful, you have to let Google know a bit more about yourself: you have to enable Search History and Location History. I think there's a separate option for access to your Gmail, too. Assuming you enable all this, you can get things like reminders for flights and shipments, it can remind you of topics you were searching for earlier, offer driving directions for places you've previously searched, movie times for movie trailers you've watched on Youtube, suggestions for nearby restaurants you might be interested in, etc.

I find it useful, but I'm completely in the Google ecosystem and don't have a problem with Google exposing all the data it knows about me.