A mouse wheel is a small cylindrical device located between the left and right buttons of a computer mouse. It allows users to scroll through documents, web pages, and other content by rolling the wheel up or down. This feature enhances navigation and improves user experience, making it easier to access information without using scroll bars. Mouse wheels can also serve additional functions, such as zooming in and out in certain applications. Some advanced mice have customizable wheels that can perform different actions, like switching between tabs or adjusting volume. Overall, the mouse wheel is a simple yet effective tool for efficient computer use.