What is called nicotine salt electronic cigarette oil

The Beginner’s Guide to Nick Salt E-Liquids Zero-Based
Nicotine salt, also known as nicotine salt e-liquid, is a relatively new vaping innovation that is particularly well-suited for pod-style vaping devices and all-in-one kits, i.e. simple beginner/intermediate devices that require no power adjustments.

Some users do use other types of devices with nicotine salts, but they keep the power and nicotine levels low. This is for comfort when the nicotine “hits” the vape, as at higher powers it hits too hard.
Avoid using nicotine salts with high levels of nicotine with devices or coils that have to run at higher wattages, this is because it will hit too much and you won’t be able to puff on it.

More and more coils are designed specifically for use with nickel salts, but you can use many conventional regular coils.
Although fundamentally similar, both types of e-juice typically contain nicotine and flavorings, with traditional-style e-juice containing so-called “freebase” nicotine, and more r “nicotine salt” e-liquids containing different ingredients, creating different types of e-cigarette experiences. Although the nicotine content may be higher, the delivery of nicotine in nicotine salt is much smoother when vaping.

Just to put this in perspective, standard e-liquid and nicotine salt e-liquid may contain the same amount of nicotine, but the nicotine salt is usually smoother and will feel different in the way the nicotine is absorbed by the body. The current maximum nicotine level in e-liquid is 20mg (0.2%).

Standard e-liquid (with free base nicotine)
The nicotine has to be very pure nicotine, which is the default form for most e-liquid manufacturers (and their traditional cigarette makers). By the way, you won’t see e-liquid labeled freebase, it’s just e-liquid or e-juice, etc. Some people call it oil, but that’s just the name people use, not oil.
In e-liquids, freebase nicotine is usually added to a mixture of VG (vegetable glycerin) and PG (propylene glycol) as the base or “carrier” liquid, along with any other ingredients like flavorings and sweeteners.

Nicotine salt e-liquid
Nicotine e-liquids contain varying amounts of nicotine and flavorings, etc., just like standard freebase e-liquids contain these ingredients. Nic salt also usually contains VG and PG, most commonly 50/50, but the amounts can vary.
Nicotine e-liquid is different in that it has added benzoic acid, which allows the nicotine content, even at higher levels, to flow more smoothly at relatively low temperatures, i.e. without the need to adjust the temperature Sucks in the same way, so it is suitable for constant/non-adjustable equipment, such as pod systems and AIO (all-in-one) kits.

To get more technical, freebase nicotine has a higher pH, which results in increased alkalinity. Increased alkalinity can lead to a worse sore throat, which often results in lower levels of nicotine inhaled.
The benzoic acid in Nick’s Salt e-liquid has the opposite effect, as it lowers the pH of the nicotine and lowers the alkalinity for a smoother hit.
Advantages of Nick Salt
The beneficial use of nickel salts depends on the needs of the user and the equipment.
E-cigarette users who are dissatisfied in some way by the lack of nicotine may benefit from using nicotine salt e-liquid, that is, vapers looking for higher doses of nicotine can use nicotine salt to deliver nicotine smoothly. Beyond that, Nick’s salts generally have less of an impact on flavor than free-base e-liquids. Generally speaking, nic salt juice has a negligible impact on flavor, and it provides a richer, more flavorful vape.
If you need a high dose of nicotine (but without the kick) and prefer a more cigarette-like experience, nicotine salts may be a good option.

Disadvantages of Nick’s Salt
There are fewer flavor options, however this is changing rapidly and probably won’t be a problem. Soon there is something for all tastes.
Users of high output sub-ohm devices/coils will need to maintain 3mg and 6mg nicotine levels in freebase e-liquids. Nicotine salts are not going to be an option for these users unless it is they who opt for low nicotine nicotine salts and keep the wattage low, which is what some are doing.
Nicotine salts are not suitable for all devices due to the temperature requirements of e-cigarettes and possibly other factors.
The smoothing effect of salty e-liquid can mask high levels of nicotine, so be careful not to over-vape (without realizing it), as this can lead to headaches and other unpleasant side effects.

Are nicotine salts right for me?
Only you can answer these questions. Saying “yes” to them is a reason to try Nick’s Salts, and “no” means sticking with standard e-liquids.
You are a heavy smoker (one or more packs per day)
Do you want a more cigarette-like experience
Do you need higher doses of nicotine when vaping
Do you want the nicotine hit to be smooth or harsh (nicotine salts are very smooth)
Other general notes, if you don’t have a device yet:
Approximately how much the equipment will cost (stick to the big brands)
How much to replace parts (say, these could be pods and coils)
How long the parts will last (average)