Nicotine Salt, also known as Nic Salt, is a type of processed nicotine used in vape juice. Many vapers find nicotine salts more satisfying than regular "freebase" nicotine.
Nicotine salt ejuice is much easier to inhale than regular eliquid due to its biocompatibility: the vape is less harsh on the throat and allows vapers to use stronger liquids. It's this ability to inhale more nicotine per puff that makes salts more satisfying.
Nic salt vape juice is particularly excellent in lower-powered devices and pod mods such as the Mi-Pod.
It's important to be careful with strong nicotine salt juice, especially in higher powered vape devices. It's easy to overdo it so take it easy when you start out.