The main difference between "famous" and "popular" is that being "famous" generally means being well-known or recognized by a large number of people, often for one's achievements or actions. On the other hand, being "popular" refers to being liked, admired, or enjoyed by a large number of people. For example, a famous actor may be known by many people, but not necessarily liked by all of them. Conversely, a popular song may be enjoyed by many people, but the artist behind it may not be widely recognized. In essence, fame is more about recognition, while popularity is more about likability or appeal.