App Clips are an iOS feature that enables users to load a smaller, lighter version of the app without requiring any installation from the App Store, providing a native experience for interacting with part of an app.
Use cases suggested by Apple include ordering take-out from a restaurant, renting a scooter, or setting up a new connected appliance for the first time. They can be initiated via NFT tags, QR codes, Safari banners, links in messages, or Place Cards in Maps. They also allow access to the app developer to present the user with notifications within eight hours of launching the App Clip.
Learn more about App Clips on Apple’s website.