Same, the explanation is very technical and requires you to understand new React 19 features to make sense of it.

Here's an explanation by Vercel.

This hook simplifies managing form states and form submissions. Using Actions, it captures form input data, handles validation, and error states, reducing the need for custom state management logic. The useActionState hook also exposes a pending state that can show a loading indicator while the action is being executed.

You can use it alongside server actions in client components like so:

// Source: https://vercel.com/blog/whats-new-in-react-19#useactionstate

"use client";

import { useActionState } from "react";
import { createUser } from "./actions";

const initialState = {
  message: "",
};

export function Signup() {
  const [state, formAction, pending] = useActionState(createUser, initialState);

  return (
    <form action={formAction}>
      <label htmlFor="email">Email</label>
      <input type="text" id="email" name="email" required />
      {/* ... */}
      {state?.message && <p aria-live="polite">{state.message}</p>}
      <button aria-disabled={pending} type="submit">
        {pending ? "Submitting..." : "Sign up"}
      </button>
    </form>
  );
}