I have often separated Street Portraiture (what I do), from Street Photography, a genre of photography involved with candid images.
Eric Kim is a prolific Street photographer, maintaining a very active blog, and offering numerous workshops around the world. See his website HERE.
While cruising the web, I came across his blog post dated March 7, 2011. It is entitled "Street Portraits vs Street Photography: What's the Difference?" See it HERE.
It is an easy read, and I hope that you'll check it out. And by all means, read the comments. They are enlightening, and in some cases, entertaining.