The term curing salts usually refers to salt with sodium nitrite, sodium nitrate, and/or potassium nitrate (saltpeter). The most common way to insure a proper level of nitrites and nitrates in your cure is to use pre-mixed curing salts. These are commonly known as tinted curing mixture (or TCM for short), tinted cure, pink salt, sel rose, Insta Cure, or Prague Powder. You can make your own curing salts by combining natural sea salt with saltpeter, but this requires a good deal of precision and a high level of fluency with the curing process itself.
Unrefined salt is also important for curing. There are natural, albeit very low, levels of nitrate in unrefined salt that subtly help with the cure, as will magnesium and other minerals.
Salting is an ancient method of preserving perishable ingredients. For most of human history, curing with salt was one of the few ways to store meat, fish, and vegetables and prevent spoiling. In doing so ancients found that the flavor changes that went along with preserving were not unpleasant. Since the advent of refrigeration, which made salt-preservation less necessary, these flavor changes are the main reason that people are attracted to salt-cured products.