The truth about PairProgramming; as opposed to the misleading page titles with names like PairProgrammingIsJustTraining, LetTheJuniorDrive (an AntiPattern), and SellPairProgrammingAsTraining (an adoption pattern that should be abandoned once PairProgramming has shown its other benefits).
This is not to say that programmers don't learn a lot from PairProgramming (they do, especially when PairProgrammingIsDoneByPeers), just that it is not usually appropriate as a training technique when skill levels differ significantly.
This is also not to say that PairProgramming can't have the same benefits as training; it can end up being very like training. But it's intended to be something other than training, and if you takes this bear and dress it up in a fish outfit, it still won't have gills.
See also PairMismatch