docs: improve explanation for "Calling a View Cell"

Author: kenjis

user_guide_src/source/outgoing/view_cells.rst

@@ -26,11 +26,13 @@ Calling a View Cell
 
 No matter which type of View Cell you are using, you can call it from any view by using the ``view_cell()`` helper function.
 
-The first parameter is the name of the class and method to call, and the second parameter is an array of parameters to pass to the method:
+The first parameter is (1) *the name of the class and method* (Simple Cell) or (2) *the name of the class* (Controlled Cell) to call,
+and the second parameter is an array of parameters to pass to the method:
 
 .. literalinclude:: view_cells/001.php
 
-The Cell method must return a string, which will be inserted into the view where the ``view_cell()`` function was called.
+The string that the Cell returns will be inserted into the view where the
+``view_cell()`` function was called.
 
 Namespace Omission
 ==================

user_guide_src/source/outgoing/view_cells/001.php

@@ -1,2 +1,7 @@
 // In a View.
+
+// Simple Cell
 <?= view_cell('App\Cells\MyClass::myMethod', ['param1' => 'value1', 'param2' => 'value2']) ?>
+
+// Controlled Cell
+<?= view_cell('App\Cells\MyCell', ['param1' => 'value1', 'param2' => 'value2']) ?>