WhatsApp is working on a new action to respond to messages called Message Reactions. After developing a shortcut to respond to messages quickly and the ability to see who reacted to messages, WhatsApp is now working on another option to react to messages. The React to Message feature will be visible to the user in the Message menu. As you have seen in the image above.
WhatsApp has told about the message reactions feature in a tweet on Twitter. The message reaction feature will be available on WhatsApp Beta Android, iOS, Web/Desktop.
WhatsApp's message reaction feature is currently under development. The message reactions feature will come on future updates on WhatsApp.