Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
Stale closure bugs are subtle because the code can look correct while reading values from an older render. They are common in timers, subscriptions, and async callbacks.
A stale closure happens when a function keeps references to values from an earlier render and later runs after those values changed. For example, an interval callback might keep using the initial count. I would fix it by including dependencies, using a functional state setter when updating from previous state, moving logic into the effect, or using a ref for mutable latest values when that pattern is appropriate.