A mouse's DPI, or dots per inch, is a measurement of how sensitive the mouse is in reference to the movement of the cursor inside the monitor. A higher DPI setting allows the mouse to make more subtle and smaller movement, but also makes it more sensitive to touch.
An overly high DPI setting on a mouse may result in a cursor zooming across the screen at the slightest touch. While mouse sensitivity can be adjusted using a range of software, the DPI is tied to the mouse's hardware capacity at production. A low-DPI mouse, for example, would have a hard time adjusting to high- sensitivity settings without significant jitter, or random movement.