Where are the commonly used characters that appear after Apple's mobile phone locks the screen?

It is a common emoticon package selected from users' short messages and iMessage chat records. Apple will automatically analyze the facial expressions used by users in SMS and iMessage chat, and add them to the "common facial expressions". When locking the screen, users can quickly use these commonly used characters by dropping down the notification center. Therefore, these commonly used facial expressions are used by users in SMS and iMessage chat, not in other applications.