Nicotine salt (nic salt), is extracted directly from the tobacco leaf. Nic salt based e-liquids are absorbed into the body far quicker than standard freebase nicotine vape juice, providing a much quicker hit to keep your nicotine cravings at bay.
In addition to this, nic salts don't deliver that severe throat hit as they stay smooth at much higher doses.
We have written a comprehensive guide to nicotine salt vs. freebase nicotine e-liquids to help you make an informed decision about which is right for you. You can read it here