Facebook push notifications are alerts or messages that are sent to users' mobile devices or web browsers to inform them about important updates, activities, or events related to their Facebook account. These notifications can include new friend requests, messages, likes, comments, event invitations, and other information relevant to the user's social activity on the platform. Users can customize their push notification settings to receive only specific types of notifications, or turn off notifications altogether. Push notifications help users stay up-to-date with their Facebook activity and engage with their friends and interests more efficiently.