An E-cigarette (electronic cigarettes or e-cigs) is a battery powered device that heats up a liquid solution (e-liquid) and turns it into a vapor that you then inhale.
A typical e-cigarette consists of a battery, an atomizer that heats the liquid and turns it into a vapor, and a cartridge that contains flavoring and (usually) nicotine in a base of propylene glycol or vegetable glycerin and water. You can buy the cartridges in many different flavors. They can contain nicotine but not all of them do.
E-cigarettes with nicotine are not approved by Health Canada for sale or use in Canada. This is because the safety, efficacy and quality of e-cigarettes are still unknown.