The "appeal to authority" is a logical fallacy where someone argues that a claim is true simply because an authority figure endorses it. This reasoning relies on the credibility of the authority rather than the evidence supporting the claim. For example, if a celebrity like Dr. Oz promotes a health product, some may believe it works just because he said so, without examining scientific evidence. While expert opinions can be valuable, it's essential to critically evaluate the evidence behind a claim. Just because someone is an authority in one field, like medicine, doesn't mean they are knowledgeable about all topics, such as nutrition. Always seek supporting evidence to make informed decisions.