Final answer:
A celebrity endorser's approval can influence consumer behavior, increase brand credibility, and leverage the endorser's attractiveness and trustworthiness to persuade consumers to purchase the product.
Step-by-step explanation:
A celebrity endorser is used in advertisements because his or her stamp of approval on a product can influence consumer behavior and increase brand credibility. This marketing strategy relies on the source credibility theory, where the persuasiveness of a message depends largely on the credibility and attractiveness of the endorser.
Well-known figures such as actors and athletes bring their own following and trust, which can be transferred to the product. This phenomenon aligns with the bandwagon effect, suggesting that if a product is endorsed by popular individuals, consumers will be more inclined to purchase it, imagining themselves to achieve a similar status or lifestyle. Brand ambassadors and social media influencers operate under a similar principle, though on different scales and platforms, their endorsements suggest that the products are worthy because they are chosen by people who are perceived as trustworthy, aspirational, or trend-setters.