How does the useState Hook work?

Direct answer

useState declares a state variable and returns the current state value together with a setter that schedules an updated render.

Counter.jsx

import { useState } from "react";

export default function Counter() {
  const [count, setCount] = useState(0);

  return (
    <button onClick={() => setCount(count + 1)}>
      Count: {count}
    </button>
  );
}

count: The state value for the current render
setCount: The setter used to request the next state
0: The initial state used on the first render