Data recovery is often seen as a cryptic and almost mystic process. The ones and zeroes inside a hard drive simply stop making their way from behind the veil of the PC tower to the fluorescent glow of the computer monitor, presumably stopped on their journey by some sort of hardware malfunction or ill-tempered electron. Whatever the case, many people think, the data is still in the hard drive, and no overly-complicated recovery technique is needed to free it from its user-induced incarceration.
The truth is that the data on a hard drive is not fundamentally different than the words written on a physical piece of paper. If the paper was somehow distorted - let's say it was burned or ripped up into tiny pieces - some words wouldn't be intelligible anymore. The "data" would effectively be lost.