[css-snappoints] More explicit definition of scroll-snap-align

Author: ChumpChief

css-snappoints/Overview.bs

@@ -419,7 +419,10 @@ Scroll Snapping Alignment: the 'scroll-snap-align' property {#scroll-snap-align}
     Animatable: no
     </pre>
 
-    The 'scroll-snap-align' property specifies how an element's scroll snap area should align with its ancestor scroll container's snapport.  The two values specify the snapping behavior in the x and y axes, respectively.  If only one value is specified, the second value defaults to the same value.
+    The 'scroll-snap-align' property specifies
+    the box's <a>snap position</a> as an alignment of
+    its <a>snap area</a> (as the <a>alignment subject</a>)
+    within its <a>snap container's</a> <a>snapport</a> (as the <a>alignment container</a>).  The two values specify the snapping behavior in the x and y axes, respectively.  If only one value is specified, the second value defaults to the same value.
 
     Issue: Should this be x/y axes, or inline/block?  Starting with x/y axes for consistency with padding/area, otherwise a writing mode change would result in a axis mismatch (since padding is physical by default).