[pitivi] help: Explain grouping better

[Alexandru Băluț <alexbalut src gnome org>]

commit 08a0620c2909973e92a92c645888433c22739ffd
Author: Andrew Clausen <andrew p clausen gmail com>
Date:   Fri Sep 11 20:19:55 2020 +0000

    help: Explain grouping better
    
    Fixes #2499

 help/C/selectiongrouping.page | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/help/C/selectiongrouping.page b/help/C/selectiongrouping.page
index 1da877fc6..56c5ca4e4 100644
--- a/help/C/selectiongrouping.page
+++ b/help/C/selectiongrouping.page
@@ -54,7 +54,12 @@
   </section>
   <section id="grouping">
     <title>Grouping and ungrouping clips</title>
-    <p>The grouping and ungrouping functions are useful when you want to add or separate audio tracks from 
video clips, or when you want to create a block of clips that you can select, edit and move all at once.</p>
+    <p>Pitivi allows you to combine</p>
+      <list>
+        <item><p>audio and video into clips, and</p></item>
+        <item><p>multiple clips into groups.</p></item>
+      </list>
+    <p>This means you can edit multiple pieces of media together, such as moving them along the timeline 
together.  This section shows you how to group and ungroup audio and video tracks within clips, and also how 
to group and ungroup multiple clips together.</p>
     <p>Grouping clips in timeline:</p>
     <steps>
       <item>