At the outset, we briefly introduce the physical phenomena and salient features of structure of the Sun. We elaborate the eruptions and emissions that occur on the Sun. On the basis of spectra and the temperature the Sun is classified as a G2V star. The proximity of the Earth with the Sun facilitates a detailed study of the surface of the Sun, atmosphere and activities which are similar in most stars. This study also provides an important opportunity on various dynamical physical processes in explicit spatial and temporal resolutions for the stars of similar masses and similar stages of evolution. There are many interesting, strange changes which take place in the interior and the atmosphere of the Sun. The Sun has a strong, complex magnetic field which can infuse the solar atmosphere with sunspots and powerful explosive events such as flares, prominence eruptions and ejection of massive particles. The Sun is a prominent star and the centre of our solar system. On the basis of spectra of solar radiations and the temperature, the Sun is classified as a G2V star. The Sun is the primary source of light and energy for life on Earth. Thus, it is all the more important to understand the physical and astronomical nature of the universe. The Sun 4.6 billion years old and is expected to live further 4.6 billion years. It has a mass of 1.99 1030 kg and radius of the order 6.95108m . The distance between the Earth and the Sun is ~ 1.491011m that is known as One Astronomical Unit (1 AU) . The surface temperature of the Sun is about ~ 5800°C