The circles serve to show the user where they can and cannot go in the model. Use a computer mouse, keyboard arrows, or just tap/touch on a smartphone or tablet (which is the BEST way to use a Matterport 3D tour, 82%+ of all real estate research is done by buyers on their smartphone by the way, so be sure to see how a Matterport looks and works on a smartphone!) to navigate from circle to circle to explore the space.
This blur spot is where the Matterport camera was placed to capture 3D data. It is blurred so that the camera tripod is not visible in the tour.