Jonathan was checking to see how much space he had used on his iPhone, and noticed a category named "other", and is wondering what it is. Leo says it's application data that's been cached like downloaded files, OS backup files, websites, ebooks, etc. Leo says not to worry about it. It's a normal category that he really can't get rid of, unless he erases everything on his phone and starts over. Sometimes deleting old text messages can free up some of that space.