translation available: Replaces translation request when all the text on the image has been translated, either via translation notes, or (for posts from before the site overhaul) translations left in the comments section. This is a signal to potential editors that the image is ready for 'shopping.
untranslated_original is VERY important because that way we don't have people trying to make English edits for stuff that already has an edited version. Editors use "translation_available -untranslated_original" to find works that haven't had English edits yet. It's not really used, or meant to be used, by anyone outside editors.