When Galileo studied them in 1610, he worked out that these black spots were moving across the surface of the Sun because the Sun was rotating. And then he suddenly realised that if the Sun rotated, then maybe the Earth rotated. In some years, there are more sunspots than in other years. The number of sunspots on the Sun reaches a maximum every 11 years or so. At these times, giant eruptions burst forth from the surface of the Sun, the aurorae are seen near both poles on Earth, electrical power grids spark and break down, and radio communications get very crackly and unreliable.
Some scientists think that the sunspots affect our weather.
From 1645 to 1715, the Sun had very few sunspots. Most of the time, this layer is vastly overshadowed by the photosphere. But if you have ever seen a total eclipse of the Sun, you will have seen the Moon surrounded by a very thin ring of bright pink light. The temperature of the chromosphere ranges from 4,000oC at the inside of the chromosphere, to 1,000,000oC where it meets the next layer out, the corona. The chromosphere has a mesh of cells that are like the granules in the photosphere - but they're much bigger at about 30,000 kilometres across.