The Sun provides an opportunity to study a star and its environment with the level of details that cannot be done for any other star. This includes high-resolution remote sensing observations as well as in-situ measurements. In the last century and since the beginning of the space era, a great amount of knowledge about the Sun, its atmosphere, and the interplanetary space has been acquired. This knowledge has helped to better understand the fundamental solar processes of solar corona heating, the acceleration of the solar wind, the generation of Coronal Mass Ejections (CMEs), and the basic mechanism that drives the solar cycle, which controls the structure of the interplanetary space and modulates the transport of cosmic rays. All of these are fundamental stellar processes that are important for other stars as well. I will review our current understanding of these processes, how the solar knowledge can be useful to understand other stars, and the processes that are still not fully understood.