It's no longer just Morton's in the round box. I need a crash course.
Iodized salt is mined from the land, as opposed to sea salt, and has iodide added to it.
It comes from the days when people who lived away from coastal areas sometimes had problems with goiters because they had no iodide in their diet. It's inexpensive, commonly available, and the one most of us know. Kosher salt also comes from the land but its structure is different - a grain looks like a snowflake whereas a grain of regular iodized salt is shaped like a cube. Kosher salt is very light and is less salty tasting because there's less of it per measure. Connoisseurs of salt like to cook with it because it's not expensive and has a pure salt taste.