Thanks for the clarification!I never use it because I've heard what Wikipedia says:
JPEG 2000 has been published as an ISO standard, ISO/IEC 15444. As of 2010, JPEG 2000 is not widely supported in web browsers, and hence is not generally used on the World Wide Web.
Interesting what it's capabilities are though. Also from Wikipedia:
While there is a modest increase in compression performance of JPEG 2000 compared to JPEG, the main advantage offered by JPEG 2000 is the significant flexibility of the codestream. The codestream obtained after compression of an image with JPEG 2000 is scalable in nature, meaning that it can be decoded in a number of ways; for instance, by truncating the codestream at any point, one may obtain a representation of the image at a lower resolution, or signal-to-noise ratio – see scalable compression. By ordering the codestream in various ways, applications can achieve significant performance increases. However, as a consequence of this flexibility, JPEG 2000 requires encoders/decoders that are complex and computationally demanding. Another difference, in comparison with JPEG, is in terms of visual artifacts: JPEG 2000 produces ringing artifacts, manifested as blur and rings near edges in the image, while JPEG produces ringing artifacts and 'blocking' artifacts, due to its 8×8 blocks.
It sounds like what they're saying is that it can be requested from a server in multiple resolutions, all from a single image.