Radial toolpaths are created from the center of the part toward the boundary. This image shows a radial toolpath example.
The center of the radial pattern is calculated automatically unless you enter a value for the Center point attribute on the Milling tab.
Not all feature shapes lend themselves to this manufacturing style. Long thin features probably are not best milled in this way. The radial term is only a rough description of the path as not all feature shapes lend themselves to a radial pattern.