Introduction
With the Message Reactions feature, you can add actions to messages that are already published. These actions can be useful for delivery acknowledgments, read receipts, and reactions such as emojis. You can provide any custom reaction as long as it's a string.
Fore more information, refer to Message Reactions.
Terminology
All message reactions in code are collectively called message reactions in the docs and the term applies both to reacting to a message (through emojis) and acting on a message (by deleting it).