https://9to5mac.com/2024/12/13/heres-everything-new-in-the-messages-app-with-ios-182/
Please read more at the above link
One of Apple’s most anticipated AI features is a core part of Messages: Genmoji.
Genmoji are built right into the standard emoji keyboard on iPhone, so you can use them across any app—but we all know Messages is the #1 place they’ll get used.
Open the emoji keyboard inside Messages, then tap the glowing smiley icon in the top-right corner to create a new Genmoji.
After Genmoji have been created, they get saved to your emoji keyboard right alongside the standard emoji.
You can send Genmoji in messages, but they can also be used as tapbacks. Just double tap a message and find your Genmoji in the tapback suggestions, or by browsing the full emoji library.