[css-shapes-2] Refine use of the word "path" in the intro (#11586)

* [css-shapes-2] Refine use of the word "path" in the introl

A "shape" is a set of commands to generate a path dynamically, rather
than them being synonomous terms.

* nits

css-shapes-2/Overview.bs

@@ -147,10 +147,12 @@ The ''shape()'' Function</h4>
 	and inherits a number of limitations from SVG,
 	such as implicitly only allowing the ''px'' unit.
 
-	The ''shape()'' function defines a path in the same way,
+	The ''shape()'' function uses a set of commands equivalent to the ones used by ''path()'',
 	but does so with more standard CSS syntax,
 	and allows the full range of CSS functionality,
 	such as additional units and math functions.
+	The commands used by ''shape()'' are dynamically turned into path segments when it is used for rendering,
+	e.g., when computing the rendered 'clip-path'.
 
 	<pre class=prod>
 		<dfn>shape()</dfn> = shape( <<'fill-rule'>>? from <<coordinate-pair>>, <<shape-command>>#)