Oh, you're talking about the lens flare? This article explains it.

The effect is a "lens flare," which happens when a camera is exposed to a bright light. In response, the lens captures some of the light as a reflection. Lens flares generally show up as little dots or circles, but during an eclipse they appear as small crescents.

So, the sun's image is blown out because it's too bright for the sensor. But the lens flare is a reflection, so it's less intense, and thus doesn't overpower the sensor.