Merge pull request rails#42510 from p8/guides/activestorage-redirect-mode

Improve "Serving Files" headings [ci skip]

Author: zzak

guides/source/active_storage_overview.md

@@ -532,16 +532,19 @@ user.avatar.purge_later
 [Attached::One#purge]: https://api.rubyonrails.org/classes/ActiveStorage/Attached/One.html#method-i-purge
 [Attached::One#purge_later]: https://api.rubyonrails.org/classes/ActiveStorage/Attached/One.html#method-i-purge_later
 
-Linking to Files
-----------------
+Serving Files
+-------------
+
+Active Storage supports two ways to serve files: redirecting and proxying.
+
+### Redirect mode
 
 To generate a permanent URL for a blob, you can pass the blob to the
 [`url_for`][ActionView::RoutingUrlFor#url_for] view helper. This generates a
 URL with the blob's [`signed_id`][ActiveStorage::Blob#signed_id]
 that is routed to the blob's
 [`RedirectController`](ActiveStorage::Blobs::RedirectController).
 
-
 ```ruby
 url_for(user.avatar)
 # => /rails/active_storage/blobs/:signed_id/my-avatar.png