Frontend & browser·State, data and re-rendering
the value lives outside the component tree and components subscribe to just the slice they read.
External store
Also calledstore, state container, subscription store
State held outside the framework, with components subscribing to changes. It avoids re-rendering a whole subtree for a value only one leaf reads, and it survives being read outside React entirely. The costs are tearing during concurrent rendering if the store is not integrated properly, and the temptation to put everything in it, which turns local state into global state nobody can trace.