Nicotine Salt, also known as Nic Salt, is a type of processed nicotine used in e-liquid. Many vapers find nicotine salts more satisfying than regular "freebase" nicotine.
Nicotine salt e-liquid is much easier to inhale than regular e-liquid 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 e-liquid is particularly excellent in lower-powered devices and pod mods.
It's important to be careful with strong nicotine salt e-liquid, especially in higher powered vape devices. It's easy to overdo it so take it easy when you start out.