Soft light
So a softbox is a device that gives soft light, right? Well, yes and no. A soft box is a light modifier, intended to make the size of the light source bigger. And all things equal, when the light source gets bigger relative to the subject, the light gets softer. And then the softbox also helps making the best use of the light by redirecting the light that would otherwise not have hit the subject.
Softbox example
Softboxes can be used for both steady light and flash light, but in the following I will assume that we are talking flashlight.
Bigger softboxes are often made as a umbrella like construction, where a set of wires defines the shape of the box. And just like an umbrella, the softbox can be folded to take up very little space when not in use. In my case the softbox is square, but many other shapes can be found.
Inside the softbox the sides of the softbox is fitted with reflective material to make the best use of the light. On the front of the softbox a white fabric is mounted and this is all lit up when the flash fires.
My softbox from Godox is also fitted with a diffuser fabric in the middle so the flash fires straight into the first layer of fabric than then diffuses the light and makes sure the light is distributed evenly within the softbox to make the final light on the front as even as possible. The ideal softbox gives a evenly lit up surface on the front of the softbox – if your softbox does a bad job here, you will see that the light is stronger in the centre than in the corners.
The rear of the softbox typically has a Bowens interface that allows you to mount the softbox directly to most light systems. In my case I used the supplied holder shown above, that connects with the softbox via the 3 pins in the Bowens interface and to the stand via a locking mechanism. In the centre of the ring above, the flash is mounted and of course it needs to be radio controlled (or in optical slave mode).
Why a softbox
As mentioned the softbox is intended to make the lightsource bigger and hence give more soft light. Relative to shooting through an umbrella, the soft box gives much more direction to the light and the light is also more evenly distributed.
Related reading
What is optical slave mode in flash photography?
What is a camera’s max flash sync speed?
What is stroboscopic flash photography?