From my (exceptionally amateur) understanding of D&D, turn undead basically allows you to turn the undead away by making them run or cower or otherwise lose their morale. Simplified, only good clerics and paladins can accomplish this.
What I don't understand is exactly how this is accomplished. The most concrete explanation I can find is from the D&D wiki, which states:
Good clerics and paladins and some neutral clerics can channel positive energy, which can halt, drive off (rout), or destroy undead.
This is a start, but it feels kind of generic: the cleric basically scares the zombie away by being really really positive.
My question is, is there any explicit explanation what actually goes through the clerics/undead when this exchange occurs, and are there any occurrences in media or text describing the process in detail?