When it comes to portraits, one of the most important decisions you can make is the choice of modifier. This great video will show you three common modifiers (softbox, parabolic umbrella, and umbrella) along with a lot of helpful example photos to show you how they will render your subject.
Coming to you from John Gress, this excellent video will show you the difference between softboxes, parabolic umbrellas, and umbrellas, with lots of examples. Lighting modifiers can quickly become quite expensive, but with good knowledge of fundamentals, you can accomplish quite a bit even with cheaper options. For example, even a cheap umbrella can make fantastic images. They can be difficult to work with because they tend to spill light everywhere, but that being said, if you can work around the drawbacks, they can produce very soft and flattering light. Plus, being super cheap, they are a great choice to take for location shoots where you might be worried about damage to your equipment. Still, they're just one of choice of many, so check out the video above for the full rundown from Gress.
If you would like to learn more about lighting for portraits, be sure to check out "Illuminating The Face: Lighting for Headshots and Portraits With Peter Hurley!"