diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index fae955f8158ad619db4bae1662abd226d6312339..ecf6fb86431914c2ec24e387a4bb6f7e07ffbfb7 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -186,6 +186,10 @@ def self.run(preloader); end
         def self.preloaded_records; []; end
       end
 
+      # Returns a class containing the logic needed to load preload the data
+      # and attach it to a relation. For example +Preloader::Association+ or
+      # +Preloader::HasManyThrough+. The class returned implements a `run` method
+      # that accepts a preloader.
       def preloader_for(reflection, owners, rhs_klass)
         return NullPreloader unless rhs_klass