The File List lists the pdf file(s) which were are added to the PDF Image Extracto. It shows the number of the raster images contained in the files, and controls if the images from the correspondent file are displayed in the Preview area.
Alternatively, click on the Show/Hide Image Preview button.
Select All button selects all the files in the list, while Unselect button unselects all the selected files.
To remove files from the list, use the Remove button.