As the name suggests, pod systems are e-cigarettes that make use of a “pod” as opposed to a traditional tank or atomizer. They ultimately do the same job: they hold the e-liquid and vaporize it to deliver vapor to you through the mouthpiece. They often have a smaller capacity than most tanks, at between 1 and 2 ml, although some pods are bigger. The pods simply push into place in the top of the device and pull out when you’ve emptied them or want to switch flavours.
Open system pods are devices that allow you to manually refill nicotine salt e-juice. Unlike the closed system devices, you can buy any bottle of nicotine salt e-liquid at varying nicotine strengths to find a flavor that suits you best.