Add clarification to CupertinoUserInterfaceLevel docs (#116371)

packages/flutter/lib/src/cupertino/interface_level.dart

diff --git a/packages/flutter/lib/src/cupertino/interface_level.dart b/packages/flutter/lib/src/cupertino/interface_level.dart
index 7d3095f..58ffe5f 100644
--- a/packages/flutter/lib/src/cupertino/interface_level.dart
+++ b/packages/flutter/lib/src/cupertino/interface_level.dart
@@ -21,7 +21,8 @@
 }
 
 /// Establishes a subtree in which [CupertinoUserInterfaceLevel.of] resolves to
-/// the given data.
+/// the given visual elevation from the [CupertinoUserInterfaceLevelData]. This
+/// can be used to apply style differences based on a widget's elevation.
 ///
 /// Querying the current elevation status using [CupertinoUserInterfaceLevel.of]
 /// will cause your widget to rebuild automatically whenever the