It grudgingly acknowledges that there are periods when the stockmarket falls but the remedy for this is simply to ride it out and even better 'buy the dips'.
The truth is that it is a self-interest doctrine - that is in the interests of the investment industry and not yours - it can be extremely damaging to your wealth (and sometimes your health) and simply is not true.
In our view 'buy and hold' is simply a 'sales pitch' and the salesmen have done a good job judging by how many investors appear to believe it!