The Apple U1 chip is new hardware that controls ultrawide band (UWB) energy transfers between devices. This enables compatible products to locate each other and exchange data in a way non-U1-enabled counterparts cannot. These new features are exclusive to the iPhone 11 Pro and Pro Max.
https://www.notebookcheck.net/Apple-develops-a-proprietary-short-range-communication-system-for-the-iPhones-11-Pro.434694.0.html