update

Author: LadyBluenotes

src/routes/reference/reactive-utilities/catch-error.mdx

@@ -44,17 +44,17 @@ Function executed inside the error boundary.
 - **Type:** `(err: Error) => void`
 - **Required:** Yes
 
-Error handler invoked when an error is thrown inside descendant scopes.
+Error handler invoked when a thrown value reaches this boundary.
 
 ## Return value
 
 - **Type:** `T | undefined`
 
-Returns the value produced by `fn`.
-If `handler` handles a thrown error, the result is `undefined`.
+Returns the value produced by `fn`, or `undefined` when a thrown value is caught and handled.
 
 ## Behavior
 
+- While `fn` runs, `catchError` establishes an error boundary for reactive scopes created inside it.
 - Only the nearest matching error boundary handles a thrown error.
 - If `handler` throws, the next parent error boundary handles that error.