The "4D" in the name of a 4D mouse refers to four directional movement. This pointing device can scroll a page both vertically and horizontally, or up/down and left/right. Having an extra direction of movement is useful not only online but also in spreadsheet applications and graphics programs. It is also good for positioning the mouse quickly in gaming, or for drawing large designs in graphics programs.
Scrolling is an extremely useful function, especially when surfing the Internet. Most websites require visitors to repeatedly click the tiny up/down window arrows or drag the vertical bar in order to scroll down the page. A 4D mouse makes this repetitive and somewhat bothersome task as easy as rolling a ball with the fingertip. A page that doesn't fit in the view horizontally can be viewed using the horizontal rollerball.
Studies have shown that repetitive motions like clicking a mouse button can cause carpel tunnel syndrome and soreness of the fingers. For those who spend only a few hours or less each day on a computer, this might not be an issue. The millions of people who spend eight or more hours a day at the screen might find this type of mouse very beneficial, however.
Aside from physical relief, scrolling with a 4D mouse is easier and faster than clicking an arrow repeatedly or dragging a scroll bar. The screen moves smoothly and can be stopped effortlessly at any position by ceasing the scrolling motion. There is no more "screen jumping" when the mouse accidentally slides off the arrow or vertical bar.
This mouse might also include programmable buttons that can be used for Back and Forward page functions or other tasks. It can be wired, wireless, or optical. Many laptops have a 4D mousepad built into the keyboard. Running the finger horizontally along the bottom edge of the pad scrolls the screen left and right, while running it up or down along the right edge of the pad scrolls vertically. Some manufacturers of keyboards offer desktop keyboards with built-in 4D pads as well.