The amount of magnetic flux that rises up to the Sun's surface varies with time in a cycle called the solar cycle. This cycle lasts 11 years on average. This cycle is sometimes referred to as the sunspot cycle. Near the minimum of the solar cycle, it is rare to see sunspots on the Sun, and the spots that do appear are very small and short-lived.
Sunspots are regions where the solar magnetic field is very strong.
In visible light, sunspots appear darker than their surroundings because they are a few thousand degrees cooler than their surroundings. Most of the visible surface of the Sun has a temperature of about 5400 degrees C, but in a big sunspot the temperature can drop to about 4000 degrees C. Sunspots come in sizes between about 2500 km and about 50,000 km. So while they are quite large, they are still much smaller than the Sun itself, which has a diameter of 1,392,000 km. Most sunspots are roughly circular in shape. Sunspots do not appear everywhere on the Sun.