Stars form from collapsing molecular gas cores. It is generally accepted that forming (low-mass) stars grow by accreting material via a disk, while accretion drives outflow which in turn impact the accreting material. The interaction of accretion and feedback determines the fate of a forming star. However, there remains a lot of unknowns about star formation. It is unclear whether massive stars form in a similar way as low-mass stars. Details about accretion and feedback processes are also not well understood. In this talk, I will introduce my theoretical and observational studies on both low and high-mass star formation. On the theoretical side, I will introduce an evolutionary model for massive star formation, and by combining with radiative transfer models, chemical models, and photoionization, we are able to predict the evolution of the IR continuum emission, the chemical abundances or development of ionized region in the massive protostellar cores. The goal is to understand the effect of the initial conditions on the evolution of the massive protostellar objects. On the observational side, I will present some of our recent studies towards both low and high-mass protostellar objects, highlighting high-resolution high-sensitivity observations using ALMA. I will focus on two main aspects: 1) accretion, including the formation of disk, disk substructures, and binary systems, and 2) feedback, including outflow launching, outflow interaction with the core, and photoionizing feedback in massive star formation. These observations have revealed so many details unexpected just a few years ago. In general, these studies showed a consistent picture of forming both low and high-mass stars. However, while putting strong constraints on existing theories, these observations also raise more questions.
