Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that exhibits promising therapeutic potential in the treatment of chronic pain, neurological disorders, and psychiatric disorders. Despite its widespread application, there remains a lack of standardized guidelines regarding the impact of various tDCS parameters (such as polarity, electrode size and placement, stimulation duration) on the induction of neurophysiological and behavioral effects. In this chapter, we present a comprehensive overview of the current understanding of tDCS encompassing its fundamental principles and common parameters, treatment protocols and precautionary measures, potential mechanisms underlying its effects, as well as influential factors. Future studies are warranted to further elucidate its mechanism of action and explore more efficacious stimulus programs.