GaN has been a very promising wide bandgap semiconductor for a long time, outperforming both Si and SiC due to its high critical electrical field and very high electron mobility. The ability to grow GaN epitaxy on silicon wafers has been both virtue and vice. It opened the possibility of 8-inch manufacturing in low-cost silicon fabs. The complex epitaxy buffer structure required to accommodate lattice mismatch when growing on Si substrates has delayed the commercial use of GaN devices. These challenges have been largely overcome and we have seen market introduction of 40V to 650V GaN devices into low and medium power range applications recently. The key application advantages of GaN are the low input and output capacitances combined with zero reverse recovery charge. These characteristics help reduce power losses in many different applications and enable efficient switching at high frequencies up to 100s of MHz. Consequently, the designers can shrink magnetics for filter circuits and reduce power losses and thus increases power density and reduces material consumption. Application engineers and the research community continue to identify an increasing number of possible applications and explore the benefits and boundaries of GaN power devices. The GaN journey as a power semiconductor solution is just at its dawn with many improvements and innovations to be realized in coming decades. This tutorial aims to introduce engineers to the basics of GaN power semiconductors and their application. We will guide you along the value chain from the basics of device physics to applications. Packaging solutions and special issues with GaN dies will be discussed. We will discuss different available driver solutions and necessary protection features and their realization to achieve the best possible operation of the different GaN devices. Testing and reliability are clearly key topics, which we will address throughout the lectures. Our team will also outline the ongoing development trends.