Message Reactions are designed to allow Facebook users to react to a message with an emoji symbol to express an emotion without needing to type out a response. Users can choose from emoji like thumbs up, thumbs down, a sad face, an angry face, a smiling face, and more.
To add a reaction to an incoming message, press and hold on the message and choose an emoji. For those who use Apple's Messages app, this action is already familiar.
The emoji reaction is added to whichever message it's attached to in the form of a small animation. Messenger Reactions work on one on one conversations and group conversations, and can be used on text, photos, stickers, videos, and more.
Also new in Messenger is "Mentions," designed to allow users to notify someone when they've been mentioned in a conversation. This is, of course, mainly useful for group conversations that have multiple participants.
A Mention can be sent by using the "@" symbol before someone's name, and the person who has been mentioned will receive a notification.
Both Mentions and Reactions are rolling out to the Messenger app today.