Reworked to respond to feedback:

- No longer solely based on manifest display modes, since browser and fullscreen are meaningful independent of manifest.
- Added a solid definition for browser and fullscreen rather than relying on that of the manifest spec.
- Added an example.

Author: mgiuca

mediaqueries-5/Overview.bs

@@ -1306,40 +1306,67 @@ Display Modes: the ''display-mode'' media feature </h3>
 	Type: discrete
 	</pre>
 
-	The 'display-mode' media feature represents the [=display mode=] of the current [=browsing context=].
-	Child browsing contexts reflect the [=display mode=] of their [=top-level browsing context=].
+	The '@media/display-mode' media feature describes the mode in which the current [=browsing context=] is
+	currently being presented to the end user.  In child browsing contexts, the [=display mode=] must
+	match that of the [=top-level browsing context=].
+
+	This feature is primarily used to determine which [=display mode=] the user agent has applied to
+	an [=application context=]. As such, the values of this feature correspond to the [=display
+	mode|display modes=] defined in [[APPMANIFEST]]. However, it can also be used in non-application
+	contexts to determine whether the viewport is in fullscreen mode.
 
-	The values of this feature correspond to the [=display mode|display modes=] defined in
-	[[APPMANIFEST]]:
 
 	<dl dfn-type=value dfn-for="@media/display-mode">
 		<dt><dfn>fullscreen</dfn>
 		<dd>
-			The [=display mode/fullscreen=] display mode.
+			The browsing context is displayed with browser UI elements hidden and takes up the entirety of
+			the available display area. The fullscreen context may have been caused by the [=display
+			mode/fullscreen=] display mode in the [=application manifest=], by the {{requestFullscreen()}}
+			method of the [[FULLSCREEN|Fullscreen API]], or through some other means (such as the user
+			manually activating fullscreen mode using the user agent's built-in controls).
+
+			Corresponds to the [=display mode/fullscreen=] display mode.
 
 		<dt><dfn>standalone</dfn>
 		<dd>
-			The [=display mode/standalone=] display mode.
+			The [=display mode/standalone=] display mode is in use.
 
 		<dt><dfn>minimal-ui</dfn>
 		<dd>
-			The [=display mode/minimal-ui=] display mode.
+			The [=display mode/minimal-ui=] display mode is in use.
 
 		<dt><dfn>browser</dfn>
 		<dd>
-			The [=display mode/browser=] display mode.
+			The browsing context is displayed using the platform-specific convention for opening
+			hyperlinks in the user agent (e.g., in a browser tab or web browser window with controls such
+			as an address bar). This should be used for non-[=application context|application contexts=]
+			that are not fullscreen.
+
+			Corresponds to the [=display mode/browser=] display mode.
 	</dl>
 
-	This media feature reflects the actual [=display mode=] that is being used on the current browsing
-	context, not necessarily the one that was requested in the web app manifest (if any).
+	<div class="example">
+		For example, the [=application manifest=] can request the [=display mode/standalone=] [=display
+		mode=] as follows:
+		<pre class="lang-json">
+			{
+				"display": "standalone"
+			}
+		</pre>
+
+		This media query can be used to determine whether the user agent has actually applied the
+		[=display mode/standalone=] mode:
 
-	Note: When a page is being displayed in a normal web browser, 'display-mode' will always have a
-	value of ''browser''. Only pages appearing in the context of an [=installed web application=] will
-	have a different 'display-mode', reflecting the way in which the application window is being
-	presented to the end user.
+		<pre class="lang-css">@media (display-mode: standalone) { … }</pre>
+
+		The user agent could set '@media/display-mode' to any of the other values, depending on the
+		actual mode currently in use. When used outside of an [=application context=], the
+		'@media/display-mode' will always be ''display-mode/browser'' or ''display-mode/fullscreen''.
+	</div>
 
 	<details class="note">
-		<summary>The [=display mode/fullscreen=] [=display mode=] is distinct from the [[FULLSCREEN|Fullscreen API]].</summary>
+		<summary>The [=display mode/fullscreen=] [=display mode=] is distinct from the
+		[[FULLSCREEN|Fullscreen API]].</summary>
 
 		The ''fullscreen'' value for [=display-mode=] is not directly related
 		to the CSS '':fullscreen'' pseudo-class.
@@ -1363,18 +1390,17 @@ Display Modes: the ''display-mode'' media feature </h3>
 
 			<pre class="lang-css">
 				/* applies when the viewport is fullscreen */
-				@media (display-mode: fullscreen) {
-					...
-				}
+				@media (display-mode: fullscreen) { … }
 
 				/* applies when an element is fullscreen */
-				#game:fullscreen {
-					...
-				}
+				#game:fullscreen { … }
 			</pre>
 		</div>
 	</details>
 
+	Note: Additional values for this media feature may be added in the future to
+	match new [=display mode|display modes=] added to [[APPMANIFEST]].
+
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