DPI stands for dots per inch. This is the resolution of the mouse and is tightly linked to polling rate in regards to accuracy of the mouse.

Higher DPI mice feed more movement data for every inch moved, and as a result, your mouse cursor moves further and is more sensitive. High DPI mice require a learning phase where you get used to using a more sensitive mouse. The benefits of this are increased reaction speed (you can turn around quicker as you have to move the mouse less) and the ability to use your mouse in a more confined space. Higher DPI mice also lessen the need for lift-off which is where you have to lift your mouse up and re-centering it to scroll further.

High DPI mice come at a premium and your standard optical mice usually run at 150-300 DPI. The minimum for a performance mouse is 800+ working its way up to and beyond 3200.

With increased DPI comes decreased accuracy, especially when try to click on a small on screen object. High DPI can be used, but aren’t the best for, say, snipers as they normally have to move slowly and accurately. As a result, most high DPI mice can change their DPI on-the-fly allowing for high speed movements and lower speed activities when the time comes. A good example of on-the-fly mice are the Saitek GM3200 and the Razer Deathadder.

High DPI mice also allow for use on less than perfect surfaces. As they ‘see’ a higher resolution image from the surface, they can often differentiate two positions between and hence reproduce movement better.