Soft Light
Light from a source that is large relative to the subject, producing shadows with gradual, feathered edges.
In depth
A large source wraps around a subject because light reaches the shadow area from many angles, so the transition between lit and unlit is gradual. The practical consequence is that softness is controlled by moving the modifier closer, not by buying a bigger one — a metre softbox at one metre is far softer than the same box at four metres.
Examples in practice
A 150 cm octabox pulled to within a metre of the face renders skin with a shadow edge several centimetres wide.