Light / glow effect

You could also google "Photoshop glow brushes" (and browse under "Images") to find an array of them.

It looks like a combination of things. I would make the shapes with the pen tool, then turn the fill opacity to 0. Then use the layer style inner glow on the shapes. Then the brush tool for the other shades. You could also use the smudge tool or path blur to blur and feather the fills. Maybe also use screen mode on some of the shapes or fills.