The chat screen is the place where Sam "lives"; it's the first screen that appears when you open the app, and it's also where you will be notified when something related to your trips comes up: anything from a weather forecast to a flight cancellation.
Most of the information is also available in other parts of the app; for instance, cancelled or delayed flights are marked as such in the itinerary. But sending a notification via Sam allows us to give you a specific piece of information at the most convenient time. That way, you won't need to check constantly if your check-in has already opened: Sam will tell you so (and provide your with the airline's check-in page URL).
Don't want to receive them all? Just go to Options and then Notification settings, where specific notifications might be turned off. For instance, you might want to receive a traffic estimation for the airport before the departure, but not when you land.
You might have noticed the little bubbles at the bottom of the chat screen. We call those "quick replies". The given number of quick replies will depend on the last notification received since they are contextual. Remember you can swipe to the right to see more options!