Studio photographers have a number of choices when creating soft light, which is diffuse light without harsh shadows. The two main choices are between softboxes — large semi-transparent devices that light shines through — or umbrellas — devices a light can bounce off of or through. Each has advantages and disadvantages, depending on the subject.
Quality of Light
Umbrellas typically produce a much broader, omnidirectional light while softboxes create a narrower path of light. Each of these can be desired, depending on the situation. Umbrellas work best when lighting a large area or a group of subjects. Softboxes work best when creating intimate lighting. A softbox may be preferable when shooting a single custom portrait, but an umbrella would be better for general soft lighting.