Using foreground to draw the viewer’s eys to your subject can add depth to a photo. Sometimes this can be done with leading lines as in the photo below. It’s also done with focus. Our eye is drawn to the sharp part of the photograph as it’s framed by the out-of-focus area.
Sometimes we may want to surprise the viewer by reversing the process. In the photo below, the focused part of the image is the foreground but is that really where we want the viewer’s attention?
This last photo uses focus and patterns to play with the viewer’s eyes. I liked this image because it somehow brought order from chaos.