Digital data in an ideal world does not change over time, does not change in transit from one location to another, and can be copied without error. But that ain't the way it is.
A file sitting on a disk will rot, not physically, but in its bits. Data over a wire or over the airwaves is subject to interference from any number of different sources, ranging from the FM station down the block to the cosmic ray station 150 light years away. Bad circuit design can cause errors; so can bad luck.
This presentation will outline the reasons why your data can decay and the mechanisms of that decay. It will focus on physical mechanisms rather than software mechanisms. You won't need to be an EE to understand it, but it would help if you've heard of electrons.