What is a Scroll Wheel in The Computer?
The scroll wheel is a small wheel found in a mouse the between the left mouse button and the right mouse button. The scroll wheel can be spun with your finger. Spinning it will "scroll" a window pane in an application that supports it.
For example, if a long text document or webpage doesn't fit in the window, you'll see scroll bars, and you can "scroll" the document either by clicking on the scroll bars or by using the scroll wheel while hovering the mouse cursor over the pane that has scroll bars attached to it.