The difference between pickling salt and regular salt is that pickling salt is pure granulated salt while regular salt which is made of (sodium chloride).
The pickling salt is different also in that the pickling salt unlike regular salt does not contain anti-caking ingredients, which can turn your pickling liquid cloudy, nor does it contain additives like iodine, which can make pickles dark.
If you want to make good pickles then you need to use pickling salt and not regular salt.
If you use regular salt the pickles or anything else you pickle with regular salt will not turn out good.
Regular salt is not pure salt while pickling salt is pure salt without any additives and regular salt usually contains other additives.
Always use pickling salt or preserving salt when pickling if you want your pickling to turn out good.