Every time I hear about Emphasis in art, I immediately think of this scene from "A View from the Top:"
Sure we're not talking about spoken language here, but it's still funny (to me). Annnnnyway...
Emphasis is the focus of the piece which is achieved by arranging the other Elements and Principles of Art in such a way that the portion you've chosen is the first thing you eye goes to upon looking at the work. This is the thing you want viewers to pay the most attention to. It is the focal point.
This art quilt is called "Tom" by Margaret Abrahamshe - she used color and quilting lines ot create Emphasis on the subject's face, which is just slightly off center in the quilt. The eye is drawn into his face and gaze.
Most commonly in quilting, we use contrast in size, shape, and color to create emphasis. Think about the accent colors you use to pop and draw the eye into your quilts.