Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sunspots appear within active regions, usually in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle.
The Swedish 1-m Solar Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands
Image: NASA's SDO Observes Largest Sunspot of the Solar Cycle (15430820129)
Image: Sunspots 1302 Sep 2011 by NASA
Image: 172197main NASA Flare Gband lg withouttext
The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately 2⁄3, or equivalently, a depth from which 50% of light will escape without being scattered.
The surface of the Sun
Solar atmosphere: temperature and density. See here for meanings of extra lines in the graph.