Microstock photography,[1] is a part of the stock photography industry. What defines a company as a microstock photography company is that they (1) source their images almost exclusively via the Internet, (2) do so from a wider range of photographers than the traditional stock agencies (including a willingness to accept images from amateur photographers and hobbyists), and (3) sell their images at a very low rate (from $0.20 - $10 USD) for a royalty-free (RF) image.
A number of microstock sites also sell vector art, and some sell audio (music) files, Flash animations and video as well as images.[2]