-- Another way of saying "Get out of the way!" ( not really )
-- Probably like the local TV news app. If you want to be notified about something, like threatening weather for instance, you can sign up for a "push notification" about the weather - or some other topic of interest.
Push notifications can update you if someone replies to one of your posts or posts in one of your followed conversations. You do not have to be on the forum itself to receive push notifications. Basically the pop up notifications you receive on your mobile phone from various apps are push notifications.