clarifying comment

lab-7/music-store-app/includes/functions.php

@@ -7,7 +7,7 @@
 (this would ideally be in includes folder)
 helps protect against XSS */
 function clean_input($data) {
-  $data = trim($data); // strips unnecessary characters from beginning/end
+  $data = trim($data); // strips whitespace from beginning/end
   $data = stripslashes($data); // remove backslashes
   $data = htmlspecialchars($data); // replace special characters with HTML entities
   return $data;