A Satin is a bird that is a Silkie in every way except for feathering. Still has black skin, five toes, feathered legs and feet, mulberry colored walnut comb, etc. Most are created by either using a polish or a cochin to introduce the smooth feathering. The resulting offspring are then continuously bred back to a Silkie over several generations. Traditionally the bird has to be 6-7 generations before it can be called a Satin.
The term Satin though is used rather loosely and many people call their 1st generation (F1) silkie crosses with any smooth feathered breed a "Satin". Technically these should be called "Silkie crosses" or "Silkie Hybrids".
There are breeders that are working on getting these birds recognized as a separate breed. They can though never be called Silkies, as they do not have silkied feathers.

This is why I choose to call my 2nd gen bird, Noa, a "Polkie" and not a Satin.