Cognitive dissonance is the buyer discomfort caused by post purchase conflict.
After the purchase, consumers are satisfied with the benefits of the chosen brand and are glad to avoid the drawbacks of the brands not bought. However, every purchase involves compromise. So consumers feel uneasy about acquiring the drawbacks of the chosen brand and about losing the benefits of the brands not purchased. Thus, consumers feel at least some post purchase dissonance for every purchase.
Cognitive Dissonance means internal state that results when individuals notice inconsistency between two or more of their attitudes or between their attitudes and their behavior.
Cognitive dissonance is a kind of balance theory proposed by the American psychologist Leon Festinger; the theory states that because we have a powerful drive towards consistency (or consonance), if we hold two psychologically inconsistent cognitions (beliefs, attitudes, values or ideas) at the same time, or if our behaviour clashes with those cognitions, we will be in an unpleasant state of tension which we are strongly motivated to reduce. As the theory deals with psychological rather than logical inconsistency, it proposes that we are not so much concerned with actually being consistent as with feeling that we are consistent.