The radius of any cylindrical object is the distance between the center and the edge of the circular face. So, radial forces refer to side-to-side forces. Axial forces refer to the up-and-down forces on the axis, which is the invisible line that runs all the way down the center of a cylinder (it’s what the cylinder would turn on).

In a scroll compressor, the top plate is fixed, and the bottom one oscillates. The forces that push them together in a sideways motion would be the axial forces, and the forces that push them together from top to bottom are the axial forces.

Compliance refers to the ability of those forces to adjust. When a small amount of liquid refrigerant gets into the compressor, the top plate can adjust itself a bit to ensure that the axial and radial forces remain sufficient enough to compress whatever is between the plates