A stock photo is a photograph taken by a professional photographer and sold on stock photo sites for use online and in print materials. (happyselfpublisher.com)
Have you used any of these free stock photo sites for eLearning, or do you have a go - to site that I didn't mention? (timslade.com)
Further, even if they are properly licensed, images from stock photo sites may limit the number of printed or electronic impressions. (toughnickel.com)