This field called Preface. Here you will be able to add any text or media using all styling options from content editor.
This field is created to show any text that users need to have before showing the main image. Preface field is optional so you can easily remove this field.
This text added in "Description" area. Here is a simple example of how Image post created with Zombify frontend uploader in Boombox Viral theme.
This post can have: Title, Excerpt, Preface, Source URL, Credit, Description, Categories and tags. Every user can easily have image post without "Excerpt", "Preface", Credit", "Source URL", Description, Category, Tags. In this post we have added image in JPEG format. Except JPEG there is an option to add PNG, GIF and image by URL.