Wiki says Ceres is a dwarf planet (or a huge asteroid, depending on your point of view), orbiting the Sun within the Asteroid Belt. It's much larger than any of the rocks it shares its orbit with, massive enough for its gravity to force it into spherical shape.
Because of its gravity and the millions of rocks it orbits with, I'd guess impacts are common. The shiny spots look like evidence of a recent impact. Question is: are the shiny patches debris from an impacting ice-teroid (I'm trademarking that name) or a glimpse of what's Ceres is actually made of underneath? Maybe Ceres is a huge ice cube with a thin coating of dust, disturbed in one place by a recent impact...