When a consumer is considering a purchase he goes through the following five stages: problem or need recognition, information search, evaluation of alternatives, purchase, and post-purchase behavior.
The initial stage in the consumer purchase decision process which involves perceiving a difference between a person's ideal and actual situations big enough to trigger a decision is called problem recognition. This is the most important stage because if a consumer does not perceive a problem or need, he/she generally will not move forward with considering a product purchase.