Final answer:
Transcranial direct current stimulation (tDCS) is an electrical stimulation technique that involves the delivery of constant, low-intensity electrical currents to specific areas of the brain in order to modulate its activity.
Step-by-step explanation:
Transcranial direct current stimulation (tDCS) is purely electrical. It involves the placement of electrodes on the scalp to deliver a constant, low-intensity electrical current to specific areas of the brain. This electrical current can modulate the brain's activity and has been studied for its potential therapeutic effects in various neurological and psychiatric conditions.