There is a drawer in a lot of kitchens with four open boxes of salt in it, bought because a recipe demanded a specific one and then abandoned. Most of those distinctions matter less than the packaging suggests, and one or two matter more than people realise. Salt is sodium chloride whichever box it comes in. What changes between them is crystal size, what else is mixed in, and where you should actually use each.
Here is the honest version, type by type.
Table salt
Fine, dense, cheap, and usually iodised. The fine grains pack tightly, so a teaspoon of table salt contains far more actual salt than a teaspoon of flaky salt. This is the source of most over-salting disasters when people swap one for another without adjusting. It dissolves fast, which makes it fine for salting pasta water or baking, where you want it gone and evenly distributed. The iodine is a genuine public-health win and does not affect flavour in normal amounts. Nothing wrong with table salt for cooking.
Kosher salt
Coarser, flakier, less dense. The big draw is control: the larger grains are easy to pinch and scatter evenly, which is why most professional kitchens season with it. It dissolves a touch slower than table salt and contains no additives. If a recipe gives salt by volume rather than weight, it probably assumes kosher salt, and the brand matters because two kosher salts can differ in density by nearly half. When in doubt, weigh it.
Flaky sea salt
Maldon and its cousins. Thin, crunchy pyramids that you crush between your fingers. This is a finishing salt, not a cooking salt. Its whole point is texture and a little burst of crunch on top of a finished dish: a steak, a salad, a chocolate biscuit, a bowl of dressed tomatoes. Dissolving it into pasta water is a waste of money. Save it for the last second before serving.
Pink Himalayan salt
The pink colour comes from trace minerals, and the marketing makes a great deal of those minerals. The honest truth is the amounts are too small to matter nutritionally. It is salt with a nice colour and a higher price. Use it if you like the look in a grinder. Do not believe the wellness claims. As a cooking salt it behaves like any coarse salt.
Iodised vs not
Iodine was added to table salt to prevent deficiency, and it quietly solved a real problem. Specialty salts, kosher and sea, usually contain none. If table salt is not your main source in the kitchen, it is worth knowing where else iodine turns up, like dairy and seafood. This is not a reason to fear fancy salt. It is a reason not to assume your pink crystals are doing a job they are not.
The one that actually changes your food
Not the type. The timing and the amount. Salting early seasons from the inside, the same principle behind a properly browned steak in the Maillard reaction, where surface salt and surface moisture decide whether you get a crust. Under-seasoning is the most common fault in home cooking, ahead of any debate about which crystal is purest. A flat dish finished with a flaky salt and a good olive oil is usually a dish that needed more salt earlier.
What we keep
One box of cheap fine salt for the pasta pot and baking. One box of kosher or a coarse sea salt for everyday cooking, where the pinch-and-scatter control earns its keep. One small tin of Maldon for finishing. That is three salts doing three jobs. The pink rock can stay in the drawer as decoration.