The only light source is the sun.

In the anti-sun angle the astronaut casts a shadow. Around it is a halo of brilliance - not a floodlight but sunlight scattering preferentially backwards (read about limb-darkening of the moon to understand what this is, how it works, and why the moon's surface behaves like this).

The Camera used is a wide angle Haselblad with huge distortion, plus the panoramic assembly of the numerous individual shots leads to further distortion. All shadows focus towards a vanishing point at the anti-sun location.

On the up-sun side, the picture is hugely stopped down (look at the step changes in brightness at each seam in the panorama). Nonetheless, a sheet of light floods the ground surface from low-angle reflection off the ground. It appears asymmetric due to different exposures to left and right of the sun and to a cross-component of slope (uphill to the right, toward the large crater rim.

If you look carefully at the ground "under" the sun, you see shadows of individual pebbles all focussing towrd the sun.

Changes in angle of the lunar surface translate to changes in illumination throughout the picture, but you must also factor-in the cylindrical geometry of the Panorama to understand relative location of objects and how they respond to illumination. (This is the sort of stuff the "lunar conspiracy" kooks misunderstood).