runOnJS
runOnJS lets you asynchronously run non-workletized functions that couldn't otherwise run on the UI thread. This applies to most external libraries as they don't have their functions marked with "worklet"; directive.
runOnUI
runOnUI lets you asynchronously run workletized functions on the UI thread.
createWorkletRuntime
createWorkletRuntime lets you create a new JS runtime which can be used to run worklets possibly on different threads than JS or UI thread. This function is supposed to be used by third-party libraries that need to integrate with worklets. The return value represents the runtime and it's supposed to be passed to C++ side using JSI (JavaScript Interface) for further operations.