[18] Add docs for useId

content/docs/hooks-reference.md

@@ -534,14 +534,50 @@ TODO: description
 ### `useId` {#useid}
 
 ```js
-const id = useId(value);
+const id = useId();
 ```
 
-TODO: description
+`useId` is a hook for generating unique IDs that are stable across the server and client, while avoiding hydration mismatches.
+
+For a basic example, pass the `id` directly to the elements that need it:
+
+```js
+function Checkbox() {
+  const id = useId();
+  return (
+    <>
+      <label htmlFor={id}>Do you like React?</label>
+      <input id={id} type="checkbox" name="react"/>
+    </>
+  );
+};
+```
+
+For multiple IDs in the same component, append a suffix using the same `id`:
+
+```js
+function NameFields() {
+  const id = useId();
+  return (
+    <div>
+      <label htmlFor={id + '-firstName'}>First Name</label>
+      <div>
+        <input id={id + '-firstName'} type="text" />
+      </div>
+      <label htmlFor={id + '-lastName'}>Last Name</label>
+      <div>
+        <input id={id + '-lastName'} type="text" />
+      </div>
+    </div>
+  );
+}
+```
 
 > Note:
 > 
-> TODO: identifierPrefix
+> `useId` generates a string that includes the `:` token. This helps ensure that the token is unique, but is not supported in CSS selectors or APIs like `querySelectorAll`.
+> 
+> `useId` supports an `identifierPrefix` to prevent collisions in multi-root apps. To configure, see the options for [`hydrateRoot`](/docs/react-dom-client.html#hydrateroot) and [`ReactDOMServer`](/docs/react-dom-server.html).
 
 ## Library Hooks {#library-hooks}