Stock photos are made to be reused: a model in a café, a marble surface, a beach at sunset, a flat lay of props. Libraries license them under terms such as royalty-free, where one fee allows broad use, or rights-managed, where the price depends on medium, region and period. Royalty-free does not mean free of conditions: many licences exclude uses such as implying that a pictured person endorses a product.
In a listing a stock photo can show context, never the product, because it does not picture the item for sale. Marketplaces commonly exclude stock and catalogue photos where buyers need to see the actual item, notably for used and second-hand goods, and some allow manufacturer images only to authorised sellers. Photos copied from another website or another seller's listing are not stock photos at all, and using them without permission infringes the photographer's rights.
Stock imagery fits the places a product photo does not cover: banners, social posts, editorial pages and backgrounds behind a cut-out product, where the licence allows composites. Because the same image is sold to everyone, a competitor may already use it. Keeping the licence, the image reference and the receipt with the file makes a later claim simple to answer, and the full licence text, not the library's summary, is the one to check.