Google Now is an intelligent personal assistant available in the Google app on Android and iOS devices. It uses your search history, calendar, and location to show you information you need in your daily life.
You may have received a Google Now message based on one or more of these factors. For example, if you've put certain tasks on your calendar, the message may be a reminder about that task. If you've indicated an interest in a certain topic, the message may be about recent news related to that topic. It may even be about local events or places of interest near your current location.
If you want to understand why you received a particular Google Now message, you can review your settings in the Google app. To do this, open the Google app and tap on the menu icon (three dots in the top-right corner) then select "Settings". From here, you can review your settings associated with Google Now, including the topics you've indicated interest in and the places you've asked to be alerted about.
Hope that helps. Let me know if you have any other questions!