Celebrity
A celebrity is a widely-recognized or famous person who commands a high degree of public and media attention. The word stems from the Latin verb "celebrere" but they may not become a celebrity unless public and mass media interest is piqued. For example Virgin Director Richard Branson was famous as a CEO, but he did not become a global celebrity until he attempted to circumnavigate the globe in a hot air balloon. Another example is Al Gore, whose environmental crusade has elevated him to celebrity status. On the other hand, mass entertainment personalities such as soap opera actors or music stars are likely to become celebrities even if the person deliberately avoids media attention.
Superstar
Superstar is a term used to refer to a celebrity who has great popular appeal and is widely-known, prominent or successful in some field. Celebrities referred to as "superstars" may include individuals who work as actors, actresses, musicians, athletes, and other professions.
According to Forbes Celebrity 100 list Tom Cruise is THE Superstar. Followed by Rolling Stones, Oprah Winfrey, U2, Tiger Woods, Steven Spielberg, Howard Stern, 50 Cent, Cast of The Sopranos, Dan Brown, Bruce Springsteen, Donald Trump, Muhammad Ali, Paul McCartney, George Lucas, Elton John, David Letterman, Phil Mickelson, J.K. Rowling and actor Brad Pitt.
Gossip
Gossip is idle talk or rumor, esp. about the personal or private affairs of others: the endless gossip about Hollywood stars. Most gossip is a distorted and far-fetched story derived from a small reality.
While gossip forms one of the oldest and (still) the most common means of spreading and sharing facts and views, it also has a reputation for the introduction of errors and other variations into the information thus transmitted. The term also carries implications that the news so transmitted (usually) has a personal or trivial nature. Compare conversation.
Some people commonly understand gossip as meaning the spreading of rumor and misinformation, as (for example) through excited discussion of scandals. Some newspapers carry "gossip columns" which retail the social and personal lives of celebrities or of elite members of certain communities.
Rumor
A rumor or rumour, is "an unverified account or explanation of events circulating from person to person and pertaining to an object, event, or issue in public concern".