Post purchase dissonance is basically an after purchase cognitive behavior. While evaluating the benefits after a purchase it is common for customers to be concerned about their purchase decision. It is caused by cognitive dissonance. Here the customer thinks that if he had purchased some other item it would have been better than the one he bought. Simply he is not completely satisfied with the purchase and is most likely to switch brands.
It is the same thing as buyer's remorse. Namely, purchasing an item and later feeling that you didn't need it, didn't need to spend the money or just was impulsive.
Congnitive consistency means people want harmony in feeling behaviour and thoughts when their is lack of harmony or conflict then there is dissonance . Disonance occurs when thheir is conflict between two cognitive factors in the case of post purchase Dissonance the conflict usualy comes about as a result of conflict between expected performance and actual performance. If expected performance is greater than actual erformance then their is post purchase disonance. Usualy higher when picking between two goods or when goods in question are high involvemenet purchases.