Salt is sodium chloride whichever box it comes from. What differs is crystal shape and size, and those change how much salt a spoon holds.
Volume is the problem
Fine table salt packs densely; flaky and coarse kosher-style salts trap air between large crystals. A tablespoon of one can weigh close to twice a tablespoon of another. A recipe measuring salt by volume is therefore only accurate for the salt its author used, which is why careful books give salt by weight or name the brand.
Where it goes matters as much as how much
Salt added early has time to diffuse; salt added at the end sits on the surface and reads as sharper. Seasoning a dish in stages and seasoning it once at the end with the same total produce different results.
Iodised, sea, rock, flaky
These describe origin and processing, not strength. Iodised salt carries added iodine; sea salt is evaporated from seawater; flaky salt is grown into thin plates. Trace minerals are present in some but in quantities too small to season with.
