An electronic cigarette is a handheld battery-powered vaporizer that simulates smoking, but without tobacco combustion. E-cigarette components include a mouthpiece, a cartridge, a heating element/atomizer, a microprocessor, a battery, and some of them have an LED light on the end. An atomizer consists of a small heating element, or coil, that vaporizes e-liquid and a wicking material that draws liquid onto the coil. When the user inhales a flow sensor activates the heating element that atomizes the liquid solution; most devices are manually activated by a push-button. The e-liquid reaches a temperature of roughly 100–250 °C (212–482 °F) within a chamber to create an aerosolized vapor. The user inhales an aerosol, which is commonly but inaccurately called vapor, rather than cigarette smoke. Vaping is different from smoking, but there are some similarities, including the hand-to-mouth action of smoking and an aerosol that looks like cigarette smoke. The aerosol provides a flavor and feel similar to tobacco smoking. There is a learning curve to use e-cigarettes properly. E-cigarettes are cigarette-shaped, and there are many other variations. E-cigarettes that resemble pens or USB memory sticks are also sold that may be used unobtrusively.

Juul Labs, Inc. is an American electronic cigarette company that spun off from Pax Labs in 2017. Juul Labs makes the Juul electronic cigarette, which atomizes nicotine salts derived from tobacco supplied by one-time use cartridges.