help center: Improve "analytics" article.

- Renames the page to "Usage statistics" (title & left sidebar).
- Adds an intro section that outlines the types of information
that can be found on the stats page.

Fixes #23449.

templates/zerver/help/analytics.md

@@ -1,9 +1,15 @@
-# View organization statistics
+# Usage statistics
 
 Zulip provides detailed analytics to help you see how you and your team are
-using Zulip.
+using Zulip. The **Organization summary** section of the usage statistics page
+includes your organization's overall usage information such as the total number
+of users, guests, messages, and storage in use.
 
-### View organization statistics
+You will also find interactive graphs that provide a detailed breakdown of
+your organization's number of active users, messages sent, messages received,
+and how these statistics have changed over time.
+
+## View organization statistics
 
 {start_tabs}
 

templates/zerver/help/include/sidebar_index.md

@@ -146,7 +146,7 @@
 * [Export your organization](/help/export-your-organization)
 * [Change organization URL](/help/change-organization-url)
 * [Deactivate your organization](/help/deactivate-your-organization)
-* [View organization statistics](/help/analytics)
+* [Usage statistics](/help/analytics)
 * [Linking to your organization](/help/linking-to-zulip)
 * [GDPR compliance](/help/gdpr-compliance)
 

templates/zerver/help/public-access-option.md

@@ -100,7 +100,7 @@ detailed below.
 * The **Organization settings** and **Stream settings** menus are not
   available to logged out visitors. However, organization settings data is
   required for Zulip to load, and may thus be [accessed via the Zulip API][info-via-api].
-* Logged out visitors cannot view [organization statistics](/help/analytics).
+* Logged out visitors cannot view [usage statistics](/help/analytics).
 
 [info-via-api]: /help/public-access-option#information-that-can-be-accessed-via-api-when-web-public-streams-are-enabled