Apple announced App Clips at WWDC 2020. They gave users quick access to certain features and functionality without having to download full apps from the App Store. Many iPhone and iPad owners love this option, and this year Apple decided to improve App Clips a bit.
Previously, developers could only add a small banner to the site, which showed that this resource has App Clips. It was not very convenient, since users had to make several taps to “unfold” the plate. iOS 15 won’t have this problem. Developers now have the ability to display the App Clips card in full screen mode. True, for this they will have to make some changes to the code. Therefore, convenient App Clips will begin to appear on sites gradually.
Source: 9to5mac