Final answer:
An active region is a highly magnetized area on the Sun's photosphere that can erupt with solar flares, plages, and prominences, especially during a sunspot maximum.
Step-by-step explanation:
The region of the photosphere of the Sun surrounding a sunspot group, which can erupt violently and unpredictably, is known as an active region. During a sunspot maximum, the number of active regions is also at maximum, indicating a period of intense solar activity.
Active regions are associated with strong magnetic fields and manifest various phenomena such as solar flares, plages, and solar prominences. These features are observed at different heights in the Sun's atmosphere but bear similar latitudes and longitudes. Importantly, plages, which are bright regions of the solar surface observed in the light of some spectral line, are notable components of active regions.