A burr grinder (sometimes referred to as a Burr Mill) is a device that is used to ground hard food items such as coffee and spices. A burr grinder uses rotating flat to conical metal disks with sharp ridges, or burrs, to evenly grind the coffee beans.  These devices can be found in electric or manual versions and higher end models will typically have a number of settings for you to select how fine or coarse of a grind you would like.