There are currently two explanations for the missing piece of the Apple logo:

The first one: derived from ancient Greek mythology.

In Greek mythology, apples are a symbol of wisdom. Adam and Eve became thoughtful after eating apples, and now they have been extended to the unknown realm of technology. Apple's logo is a bitten apple, which shows their courage to march into science and explore unknown areas.

The second type: derived from the legend of Alan Turing, the father of computers.

Alan Turing is known as the father of computer science. The famous Turing machine model he proposed laid the foundation for the logical working method of modern computers. But he was a well-known homosexual and was persecuted for his homosexuality. Turing died from eating an apple soaked in cyanide solution. Many believed his death was intentional and ruled his death a suicide. But his mother strenuously argued that his death was an accident because he accidentally piled chemicals in the lab. The Apple logo is sometimes mistakenly believed to be derived from the half-apple that Turing bit when he committed suicide.

With the development of Apple's corporate culture, Apple officials are more inclined to the first statement, in order to emphasize Apple's unremitting pursuit of excellent technology.