Hey JR - this term was coined when a few of us starting talking about what elements in our outfits made that outfit work for us and made us feel good. Not individual items like this particular blouse or that particular skirt, but elements such as structure or colour.
I was working on honing in on my personal style and started to realize there were certain things that made me feel good. My rubric includes: structure, colour, classic, retro/vintage and urban. When I include one or more of these elements into an outfit, this is when I tend to feel the most like "me".
I hope this helps - I know Rae and Goldenpig (Natalie) also have rubrics, as well as a few others that I can't think of off the top of my head.