At the core, I have the mind of an engineer. I like objective things that are nicely organized and structured. I try to put my world this way. So, when I wanted to know the difference between a strobe and a flash I figured it would be fairly straight forward. As it turns out, there is ambiguity in the terminology and its use – so for the newbies it is confusing.
The reason there is a lack of clarity in what a strobe is and what a flash is, is because there is a lack of clarity between what a strobe is and what a flash is. (kind of like the verse in the bible that says “How to get wisdom. Get wisdom.”).
At the highest level, the term Flash is used to describe any artificial light that is part of the camera system. So, this would encompass the pop-up flash on your camera, that fancy (and expensive) speedlight on the camera or placed off the camera on a stand, or even the professional lights in the photography studio.
However, the term Strobe is also used referring to many of the same devices that flash is used to identify. I’ve never heard anyone call the pop-up flash on their camera a strobe, but beyond that …. yeah.
It would be too simple for Strobe and Flash to be completely interchangeable terms. Nope. In a lot of contexts, strobe and flash mean different things.
I’ve heard of two origins for the term strobe. First, strobe is short for stroboscope, or stroboscopic – an intense flashing/pulsing light. Most everyone has seen these used to freeze motion in a “freeze frame” way. The second origin is that “Strobe” was the brand name of a studio flash (later changed to Strobex, and now no longer in business)
Given the origins of the term Strobe, it makes sense for it to be used to describe flashes in general, and more specifically studio flashes. Knowing this, you can tell by the context in which the term Strobe is used, what it is actually referring to.
In most cases, strobes are referring to the high-power, dedicated, AC powered studio flash units – or the same units with dedicated battery packs.
Speedlights, those add-on flash units that can be placed on the top of your camera in the hot-shoe or placed on flash stands for use off-camera, are usually called flashes or speedlights, but are occasionally referred to as strobes.
Pop-up flashes or flashes that are only for use on the camera itself are always called flashes.
Those are the generalities for using the terms flash and strobe. It is kind of like a continuum, where the context of the discussion or article determines which term is correct. On one end is the pop-up flash, on the other end is the high-end studio lighting – with lots of stuff in between. It seems that when you are nearer the side of the continuum where the device is on-camera, the devices are referred to as flashes. If you are closer to the studio lighting setup, then they are more often referred to as strobes.
The next question would be when is it better to use a “Flash” vs a “Strobe”. Here is a great article by Scott Kelby on this. It is worth a read. http://scottkelby.com/2009/studio-strobes-vs-small-off-camera-flashes/