The Fracture noise rollouts have parameters which allow you to tune how fracture meshes are displaced, prior to fracture. These displacements are what create fracture details.
Fracture noise A/B are two separate levels of noise that you can apply to any fracture mesh (common usage of the two levels are: one level for larger displacements and one level for smaller, more detailed displacements - layered together for more control over the overall shape of the noise through the fracture mesh).
Fracture shell noise specifically applies to fracture meshes that have been extruded with the shell settings available in the Fracture meshes rollout. Fracture noise A/B displace fracture mesh vertices directly, whereas Fracture shell noise varies the distance that a shell operation will extrude a fracture mesh, at a given point in space.
Radial random walk specifically applies to the radial lines of radial fracture patterns.
The individual noise parameters themselves are identical to other noise parameters found throughout tyFlow (with the exception of some Multifracture-specific noise presets available in the noise rollouts, from the “Presets” menu button), and are not outlined further here.