Knowledge is a familiarity with someone or something, which can include facts, information, descriptions, or skills acquired through experience or education. It can refer to the theoretical or practical understanding of a subject. It can be implicit (as with practical skill or expertise) or explicit (as with the theoretical understanding of a subject); and it can be more or less formal or systematic. In philosophy, the study of knowledge is called epistemology, and the philosopher Plato famously defined knowledge as "justified true belief." However no single agreed upon definition of knowledge exists, and there are numerous theories to explain it. The following quote from Bertrand Russell's "Theory of Knowledge" illustrates the difficulty in defining knowledge. "The question how knowledge should be defined is perhaps the most important and difficult of the three with which we shall deal. This may seem surprising: at first sight it might be thought that knowledge might be defined as belief which is in agreement with the facts. The trouble is that no one knows what a belief is, no one knows what a fact is, and no one knows what sort of agreement between them would make a belief true. Let us begin with belief."

Selena Marie Gomez (born July 22, 1992) is an American actress and singer best known for portraying Alex Russo in the Emmy Award-winning Disney Channel television series Wizards of Waverly Place. She subsequently ventured into feature films and has starred in the television movies Another Cinderella Story, Wizards of Waverly Place: The Movie, and Princess Protection Program. She made her starring theatrical film debut in Ramona and Beezus.

Her career has expanded into the music industry; Gomez is the lead singer and founder of the pop band Selena Gomez & the Scene, which has released three RIAA Gold certified studio albums, Kiss & Tell, A Year Without Rain, and When the Sun Goes Down, spawned three RIAA Platinum certified singles, "Naturally", "Who Says" and "Love You Like a Love Song" and charted four No. 1 Billboard Hot Dance Club Songs. Gomez has also contributed to the soundtracks of Tinker Bell, Another Cinderella Story, Wizards of Waverly Place, and Shake It Up after signing a record deal with Hollywood Records.