  Star formation is a complex multi-scale phenomenon that is of significant
importance for astrophysics in general. Stars and star formation are key
pillars in observational astronomy from local star forming regions in the Milky
Way up to high-redshift galaxies. From a theoretical perspective, star
formation and feedback processes (radiation, winds, and supernovae) play a
pivotal role in advancing our understanding of the physical processes at work,
both individually and of their interactions. In this review we will give an
overview of the main processes that are important for the understanding of star
formation. We start with an observationally motivated view on star formation
from a global perspective and outline the general paradigm of the life-cycle of
molecular clouds, in which star formation is the key process to close the
cycle. After that we focus on the thermal and chemical aspects in star forming
regions, discuss turbulence and magnetic fields as well as gravitational
forces. Finally, we review the most important stellar feedback mechanisms.

Astrophysics of Galaxies;Solar and Stellar Astrophysics