A questions that comes up from time to time is what does axial or radial leaded mean? This is calling out how the leads comes out of the component. Axial leaded components will have a lead or multiple leads coming out of each end of the component.
Structurally, using a form of carbon powder mixed with an insulating material, which does not conduct electricity at all, forms most through hole resistors. This is mixed with a paste or resin to create a solid inner core of the resistor, the conductive path. The ultimate resistance of the device is determined by how much carbon fiber there is relative to the insulating material within the core, or the ratio between them. The more carbon, the lower the resistance. To protect the core, a plastic shell is often placed around it, and two thin wire terminals attach to each end.
Axial leaded resistors are typically simple cylindrical components with a long terminal pins on either side which can be bent to conform to a variety of hole layouts on a PCB. Often they are color coded with an industry-standard code that displays the ohmage rating of the device. They have a wide range of variability, with the same package sizeable to accommodate an impedance of less than 1 ohm up through 10s of millions.
Radial which many people think is the shape of the component is actually calling out that the leads are coming out the same side of the component. Radial lead type of thin film resistors has the tightest resistance tolerance and the smallest TCR, and is mounted on the insert type PCB board.
