The Mighty Mouse was the first Apple mouse to have multiple buttons. The buttons consisted of two touch-sensitive areas on the top of the mouse and two “squeeze areas” on the sides of the mouse. Because it had no physical buttons, the entire body of the mouse could be clicked. The top of the mouse also had a mini free-spinning track ball that allowed scrolling in any direction.
The Mighty Mouse was opaque white with light gray touch-sensitive squeeze areas. The mini trackball on top was also light gray.
Mighty Mouse makes a sound when the scroll ball is rolled that is produced by a tiny internal speaker in the mouse. The sound cannot be disabled by settings.
In October 2009, Apple renamed the Mighty Mouse the “Apple Mouse” due to legal issues regarding the name. Although Apple had licensed the Mighty Mouse name from CBS (a cartoon character originating in 1942), another company had been selling a “mighty mouse” product before Apple. This is an example of Apple’s sometimes-confusing naming practices. in this case, Apple returned to using the name of a previous product (from 2003) that had a different design and different features.
Source: Wikipedia.com, arstechnica.com