Sticker Maker allows iPhone X owners to turn selfies into custom animated GIF stickers, which you can then share in Apple iMessage and any other texting app. In the Giphy app this feature can be found in the "Plus" symbol tab, tap "Sticker", and then you can take your photo. The image has to be uploaded to a Giphy account so you can use it across Giphy's connected apps and keyboard extension.
Giphy's own GIF features have powered other apps before, including GIF sticker search in Instagram. The company's keyboard extension also works with Apple iMessage, similar to apps like GIF Keyboard. Although Apple's iMessage App Store introduced app-based alternatives, many keyboard extensions like these have remained popular over the years.