Minecraft wiki entry for Raw_JSON_text_format, associated text: The text component.
 translate: A translation identifier, corresponding to the identifiers found in loaded language files. Displayed as the corresponding text in the player's selected language. If no corresponding translation can be found, the identifier itself is used as the translated text.
 with: Optional. A list of raw JSON text components to be inserted into slots in the translation text. Ignored if  translate is not present.
A raw JSON text component. If no component is provided for a slot, the slot is displayed as no text.