document the differences among the example themes

(cherry picked from commit 54668ac)

Documentation/Configuration/Reference/Index.rst

@@ -57,15 +57,17 @@ theme
    my-theme
 
 :aspect:`Description`
-   Name of the theme. It is used to extend the :ref:`resourcesBasePath` to create a full path to to the default themes.
+   Name of the theme. It is used to extend the :ref:`resourcesBasePath` to create the full path to templates and assets.
 
-   The shipped default themes are:
+   The shipped default themes are (each showcase the functionality a bit differently):
 
-   * `bootstrap3-banner`
-   * `bootstrap3-modal`
-   * `bootstrap4-modal`
+   * `bootstrap3-banner`: needs Bootstrap 3; uses a text link "settings" instead of a button; shows "Accept all cookies" only after opening the settings; uses custom accordion CSS to show opened/closed state (+/x) and enhanced checkboxes
+   * `bootstrap3-modal`: needs Bootstrap 3, uses custom CSS on the "settings" button and the accordion to show opened/closed state (⯈/⯆), shows the checkboxes inside left of the accordion header
+   * `bootstrap4-modal`: needs Bootstrap 4, uses custom CSS on the "settings" button and the accordion to show opened/closed state (+/x), shows the checkboxes inside right of the accordion header
 
-   Of course you can use your own custom theme.
+   You can check out the :ref:`demo` or see the :ref:`screenshots` to get an idea.
+
+   Of course you can use your own custom theme (see :ref:`customization`).
 
 
 .. _links.dataProtectionDeclarationPid:

Documentation/Introduction/Index.rst

@@ -75,7 +75,9 @@ which triggers a message inside the popup (in the "marketing" group) when enable
 Screenshots
 ===========
 
-You can click on the screenshots to open the full resolution.
+You can find some notes about the differences among the example themes here: :ref:`theme`.
+
+(Click on the screenshots to open the full resolution.)
 
 .. figure:: ../Images/bs4-modal-initial.png
    :class: with-shadow