GSM Arena page mentions a user can react to an upload with seven emoticons reaction: love, smile, wow, sad, angry, yes, and no.
When someone reacts to upload, the owner will receive animated messages, as well as notification when the recipient does not open Messenger.
Features of this reaction is applicable to all types of messages: text, stickers, videos, images, GIF, and emoji.
This button also applies to private and group conversations.
Meanwhile, mention features, such as social media, simply add the symbol "@" in front of the user name so that she noticed immediately that created the message.
People who are at-mention will receive a notification that you send him a message.