A live center has internal bearings and the conical contact surface rotates with the workpiece. A dead center is just a stationary point, with rubbing contact between the cone and the workpiece. Revolve with their workpiece. They hold ball bearings inside that allow the center to prevent wearing to its ends. Live centers allow more force,higher turning speeds (without separate lubrication) and tighter gripping on work than plain centers, further reducing sideways movement during turning operations.