Mouse wheel side-clicks
You won’t find this on all mice, but some mouse wheels can be tilted left or right to provide further functions. Most often, this is used to scroll documents and apps left or right.
Open the Control Panel and click Mouse. On the Wheel tab, you may find an option for horizontal scrolling by tilting the wheel. You can choose how many characters at a time to scroll.
Can your mouse wheel tilt? Check the mouse settings in the Control Panel