diff --git a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h
index fac783f87f3..0ace741ccab 100644
--- a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h
+++ b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h
@@ -17,6 +17,17 @@
 #include "flutter/shell/platform/darwin/ios/ios_surface.h"
 #include "flutter/shell/platform/darwin/ios/ios_surface_gl.h"
 
+/// UIViews that are used by |FlutterPlatformViews| to present Flutter
+/// rendering on top of system compositor rendering (ex. a web view).
+///
+/// When there is a view composited by the system compositor within a Flutter
+/// view hierarchy, instead of rendering into a single render target, Flutter
+/// renders into multiple render targets (depending on the number of
+/// interleaving levels between Flutter & non-Flutter contents). While the
+/// FlutterView contains the backing store for the root render target, the
+/// FlutterOverlay view contains the backing stores for the rest. The overlay
+/// views also handle touch propagation and the like for touches that occurs
+/// either on overlays or otherwise may be intercepted by the platform views.
 @interface FlutterOverlayView : UIView
 
 - (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;