[form] Refine onSubmit/action framing and address review

Author: aurorascharff

src/content/reference/react-dom/components/form.md

@@ -50,7 +50,9 @@ To create interactive controls for submitting information, render the [built-in
 
 ### Handle form submission with an event handler {/*handle-form-submission-with-an-event-handler*/}
 
-Pass a function to the `onSubmit` event handler to run code when the form is submitted. By default, the browser sends the form data to the current URL and refreshes the page, so call [`e.preventDefault()`](https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault) to override that behavior. Read the submitted data with [`new FormData(e.target)`](https://developer.mozilla.org/en-US/docs/Web/API/FormData).
+Pass a function to the `onSubmit` event handler to run code when the form is submitted. By default, the browser sends the form data to the current URL and refreshes the page, so call [`e.preventDefault()`](https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault) to override that behavior.
+
+This example reads the submitted values with [`new FormData(e.target)`](https://developer.mozilla.org/en-US/docs/Web/API/FormData), which collects every field by its `name`. This keeps the inputs [uncontrolled](/reference/react-dom/components/input#reading-the-input-values-when-submitting-a-form). If you instead [control an input with state](/reference/react-dom/components/input#controlling-an-input-with-a-state-variable), read from that state on submit rather than from `FormData`.
 
 <Sandpack>
 
@@ -61,7 +63,8 @@ export default function Search() {
     e.preventDefault();
 
     // Read the form data
-    const formData = new FormData(e.target);
+    const form = e.target;
+    const formData = new FormData(form);
     const query = formData.get("query");
     alert(`You searched for '${query}'`);
   }
@@ -79,11 +82,11 @@ export default function Search() {
 
 <Note>
 
-Reading form data with `onSubmit` works in every version of React and gives you direct access to the [submit event](https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/submit_event). The `action` prop, described next, builds on this with extra features like automatic form resets, pending states with [`useFormStatus`](/reference/react-dom/hooks/useFormStatus), and [Server Functions](/reference/rsc/server-functions).
+Reading form data with `onSubmit` works in every version of React and gives you direct access to the [submit event](https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/submit_event), so you can call `e.preventDefault()` and read the data yourself. Passing the function to the `action` prop instead runs the submission in a [Transition](/reference/react/useTransition). React then tracks the pending state, sends thrown errors to the nearest error boundary, and lets the form work with [`useActionState`](/reference/react/useActionState) and [`useOptimistic`](/reference/react/useOptimistic). An `action` can also be a [Server Function](/reference/rsc/server-functions), which `onSubmit` does not support.
 
 </Note>
 
-### Handle form submission with an action {/*handle-form-submission-with-an-action*/}
+### Handle form submission with an action prop {/*handle-form-submission-with-an-action-prop*/}
 
 Pass a function to the `action` prop of form to run the function when the form is submitted. [`formData`](https://developer.mozilla.org/en-US/docs/Web/API/FormData) will be passed to the function as an argument so you can access the data submitted by the form. This differs from the conventional [HTML action](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/form#action), which only accepts URLs. Unlike `onSubmit`, an `action` runs in a [Transition](/reference/react/useTransition) and calling `e.preventDefault()` isn't needed. After the `action` function succeeds, all uncontrolled field elements in the form are reset.