What are the specific differences between low-salt and 2g salt diet?

Both are low: There are several reasons to be on a low salt diet. Only about 15-20% of people are 'salt sensitive' and need to restrict salt or they will get high blood pressure. There are excellent studies that show that a diet that is very low in salt leads to an increase in mortality. If you need a low salt diet ask your doctor what salt intake is appropriate for your condition.

Less than 2 g: low salt is less than 2 grams of salt a day. Ingredients are listed in order of the amount the food contains. Avoid foods that list salt near the top of the list of ingredients. A product with less than 100 mg of salt per serving is good. You can aim for 1500 mg or less of salt daily and still provide the amount of salt your body needs.