Stars form from molecular cloud cores by gravoturbulent fragmentation. Understanding the angular momentum and the thermal evolution of cloud cores thus plays a fundamental role in completing the theoretical picture of star formation. This is true not only for current star formation as observed in regions like the Orion nebula or the ¿-Ophiuchi molecular cloud but also for the formation of stars of the first or second generation in the universe. In this thesis we show how the angular momentum of prestellar and protostellar cores evolves and compare our results from hydrodynamical simulations with observed quantities. We find that collapse induced by gravoturbulent fragmentation is accompanied by a substantial loss of specific angular momentum. This eases the "angular momentum problem" in star formation. The distribution of stellar masses at birth (the initial mass function, IMF) is another aspect that any theory of star formation must explain. Our investigation generally supports the idea that the distribution of stellar masses depends mainly on the thermodynamic state of the gas.