On Android, it often kicks off notifications when things are relevant to your situation. For example, it learns where home & work are (based on where I spend time during day or night). When travel time back home at rush hour is bad, it sends a notification to say I might want to leave earlier.
If you put a location in a Google calendar item, it will keep tabs on traffic and notify you when you should leave for your appointment.
If your search history shows you're searching for a sports team often, it'll have a standing card with that team's scores & schedules.
Google Now is connected to your Gmail and can pop up notifications for shipments, flights, restaurant reservations, etc based on receipts and boarding passes in your inbox.
If you put a location in a Google calendar item, it will keep tabs on traffic and notify you when you should leave for your appointment.
If your search history shows you're searching for a sports team often, it'll have a standing card with that team's scores & schedules.
Google Now is connected to your Gmail and can pop up notifications for shipments, flights, restaurant reservations, etc based on receipts and boarding passes in your inbox.