The breakdown of most conventional theoretical techniques is a hallmark of strongly correlated many-body systems. In particular, phases with fractional excitations and unconventional quantum phase transitions are not accessible by perturbative methods. There is thus a compelling need for alternative techniques. Among the most powerful tools available to study such systems are so-called dualities, which state that two apparently distinct theories are, in fact, one and the same. Crucially, many dualities relate systems that are hard to study to those that are much simpler and thus allow understanding the former by analyzing the latter.