The Planet tutoral...

don't for get that some gradients can give "depth" to objects and make it look more round :D

"I loaded a selection of the circle and, on a new layer, used the radial gradient tool, to create the blend from black to transparent you see to the left."

I don't really understand this part. I know where the radial gradient tool is, however, I don't understand the rest he says. Selection of the circle? *Is confused*

while he had the layer-with-the-circle selected he loaded the layer as a selection (Select/Load Selection...)

then he made a new layer

then he used a black->transparent gradient