These libraries contain high and low-res photographs intended for artists to use as raw material and generate content from textures, collages, matte paintings, illustrations, etc.
Photographs are priced at less than two cents per image and sold in bundles of 100 or more ($2).
The only thing you can’t do with these is sell or give away the images or claim them as your own. Only derivative works are allowed. Just like instrument and sound libraries are used by digital musicians.
As libraries grow, price will increase by $1 for every 100 new images added. But these updates will come to you free via email updates. So invest early and save BIG in the long run.