Alternatively referred to as a Microsoft mouse, wheel mouse or scroll mouse, the IntelliMouse is a mouse brand first developed by Microsoft in 1996 that has a wheel between the left and right mouse buttons that enables the user to scroll up and down using the wheel instead of having to use the vertical scroll bar. In addition to being able to scroll, these mice also have the ability to use the wheel as a button by pressing down on the wheel. An example of how this button could be used is using the wheel to open a link in a tab. In the below picture, is an example of what the Microsoft IntelliMouse looks like.
Because of the wide popularity and acceptance, this type of mouse has become a standard type of mouse used with all new computers. Although "IntelliMouse" is a Microsoft Trademark, wheel mice are developed by every mouse manufacturer today.
Also see: Mouse definitions