Semiconductor electrodes (SCEs) play a crucial role in (photo)electrochemistry, particularly in devices used for photoelectrochemical energy conversion and storage applications. Despite many alluring applications, atomic-scale understanding on the factors defining the (photo)electrochemical performance of SCEs remains far from that of metallic electrodes as SCEs exhibit more nuanced electronic structure features due to the presence of a band gap, possible polaronic and surface states, and doping effects, for instance. ] Also, the electrode-electrolyte interfaces are more complex than those on metallic electrodes due to the pronounced role of surface states and acid-base chemistry on oxide surfaces, for example. Furthermore, the low number of charge carriers leads to features such as the spatially extended space-charge region (SCR) and band bending. Finally, in the case of electrochemistry, all these effects depend on the applied electrode potential. Overall, simulating these electronic and structural effects requires the use of more refined electronic structure methods and atomistic models than needed for metals.