Salt nicotine is refined differently from traditionaly refined nicotine It is designed to give an instant hit but be a smoother vape than traditional nicotine at the same strength. So an 10mg will feel like a 3mg on the throat and a 20mg will feel like a 6mg on the throat but with the head feel and strength on a higher nicotine. This helps satisfy those that need higher nicotine but find traditional nicotine harsh.
Salts come in 10ml bottles flavoured and usually in strengths of 5mg, 10mg & 20mg. There are also salt nicotine shots for adding to short fills