Animation Worklet is a Houdini primitive that provides extensibility point for Web Animations and enables rich high-performance scripted animations which can (potentially) run off main rendering thread. It allows you to write rich imperative animations that run at the device's native frame rate for jank-free smoothness, make your animations more resilient to main thread jank. Future enhancement will enable such animations to also respond to user input (such as touch and scroll).
Docs: https://developers.google.com/web/updates/2018/10/animation-worklet