An image that is a cropped portion of a larger picture.
It's not uncommon for artists on Twitter to post both the full-size picture and a crop, in order to play around twitter's cropping mechanism. Sometimes the cropped version is of higher resolution than the equivalent portion of the full picture, in which case it makes sense to upload both images. Generally, you should make the cropped post the child post, even if it is of higher resolution than the uncropped post.
It is also possible that the full size image is only available as a paid reward.
