[css-display-3] Improve intro to 'order'.

Author: fantasai

css-display-3/Overview.bs

@@ -951,9 +951,6 @@ Toggling Box Generation: the 'display-or-not' property</h2>
 <h2 id='order-property'>
 Display Order: the 'order' property</h2>
 
-	Boxes are generally displayed and laid out in the same order as they appear in the source document.
-	In some layout modes, the 'order' property can be used to change this ordering.
-
 	<pre class='propdef'>
 	Name: order
 	Value: <<integer>>
@@ -968,7 +965,16 @@ Display Order: the 'order' property</h2>
 		flexible-order.html
 	</wpt>
 
-	The 'order' property controls the order in which
+	Boxes are generally displayed and laid out
+	in the same order as they appear in the source document.
+	In some [=formatting contexts=],
+	the 'order' property can be used to rearrange the order of boxes
+	to deliberately create a divergence
+	of the logical order of elements
+	and their spatial arrangement on the 2D visual canvas.
+
+	Specifically,
+	the 'order' property controls the order in which
 	[=flex items=] or [=grid items=] appear within their container,
 	by assigning them to ordinal groups.
 	It takes a single <dfn value for=order><<integer>></dfn> value,