With the increasing penetration of inverter-based resources (IBRs) in electrical grids - owing to the global push towards decarbonisation of the grid - power system harmonics have had a resurgence as a hot topic of discussion. These non-linear forms of load and generation have fundamentally transformed the grid and given rise to many challenges, including in managing the quality of power supply. The aim of this presentation is to try to demystify the complex concepts related to harmonics.