A data transformation is information preserving if the original data could, in principle, be recreated from the transformed data. In audio processing Fourier transform are often used to transform a signal into {[frequency space}}, but a reverse trabsform can recreate the orginal sound. Compression algorithms are often classified into lossless compression which is information preserving and lossy compression, for example in JPEG format, where some of the details of the image are irretrevably lost.
Used on Chap. 14: page 336