Minecraft wiki entry for Raw_JSON_text_format, associated text: Translations can contain slots for text that is not known ahead of time, such as player names. When displaying the translated text, slots will be filled from a provided list of text components. The slots are defined in the language file, and generally take the form %s (displays the next component in the list), or %3$s (displays the third component in the list; replace 3 with whichever index is desired).[note 3] For example, the built-in English language file contains the translation "chat.type.advancement.task": "%s has made the advancement %s",.