Now that the Dawn spacecraft is closer to Ceres, we can see the bright spots more clearly, and they are composed of several smaller spots. The image above was taken on May 4, 2015 from a distance of 13,600 kilometers. Dawn is now mapping Ceres.
JPL is still not offering any official guesses as to the nature of the spots, but planetary scientists are pretty convinced they must be ice. Ice was expected at Ceres. But the unsolved problem is: why is ice showing up so brightly in that one place on the surface? Something special must have happened, or be happening, there.
Even better images will be coming in future orbits.