A Contact Sheet is a sheet of photographic paper displaying small-scale versions of photographic images for quick review.
This command-line program starts in a specified folder and searches for photos within that folder and all subfolders (and so on, recursively down through the tree of folders). It generates a contact sheet for each folder and saves some information about the photos it has seen, so that it can skip folders which have not changed the next time that you run it. Each sheet is stamped with the time & date, plus the location of the folder. The small images are each 230 pixels in width (and are vertically scaled in proportion) and each has the image filename displayed below it.