MDL-25151 new help string thanks to Mark Nelson for reporting it missing

question/type/random/lang/en/qtype_random.php

@@ -24,8 +24,9 @@
  */
 
 $string['configselectmanualquestions'] = 'Can the random question type select a manually graded question when it is making its random choice of a question from a category?';
-$string['editingrandom'] = 'Editing a Random question';
+$string['editingrandom'] = 'Editing a random question';
 $string['random'] = 'Random';
+$string['random_help'] = 'A random question is not a question type as such, but is a way of inserting a randomly-chosen question from a specified category into a quiz.';
 $string['randomqname'] = 'Random ({$a})';
 $string['randomqplusname'] = 'Random ({$a} and sub-categories)';
 $string['selectmanualquestions'] = 'Random questions can use manually graded questions';