Direct current (often abbreviated as DC) is electricity that flows steadily in one direction, like water flowing downstream in a river. In contrast, the electricity from wall outlets in your home uses alternating current (AC), which rapidly switches direction back and forth, like a wave sloshing back and forth in a bathtub.

Batteries produce direct current. When you put batteries in a flashlight or a remote control, electrons flow in a single, steady path from the negative end to the positive end, powering your device. Solar panels also generate direct current when sunlight hits them.

Direct current was championed by inventor Thomas Edison in the 1880s during the famous “War of the Currents,” when he competed against George Westinghouse and Nikola Tesla, who promoted alternating current. While alternating current eventually won for long-distance power transmission (it's easier to send over power lines), direct current remains essential today. Your laptop, phone, and tablet all run on DC power. That's why their chargers have bulky adapters: they convert the AC from your wall outlet into the DC your devices need.

Interestingly, many modern technologies are bringing DC back into prominence. Electric cars run on direct current from their batteries, and some engineers are now designing DC-powered buildings and microgrids because they work better with solar panels and battery storage systems.