A conical burr grinder is a style of coffee grinder (or any grinder really) that uses a sets of grinding burrs that are cone-shaped. The burr is the part of the grinder that crushes coffee in slow, low-RPM way (as opposed to a blade grinder, which is more of a blender). The cone-shaped burrs are very effective while being much smaller and cheaper to produce than the flat burrs found on most professional grinders.