What is the relationship between salt and iodine?
Iodine is commonly added to table salt, hence the term "Iodized".

This is purely a public health issue, much like fluoridation of water.   The human body needs small quantities of Iodine for good health, and salt was the method chosen to give it to us.  Just as fluoride is added to water, and Vitamin D is added to milk.  It actually has nothing to do with the product, it's just a convenient carrier.

See: http://en.wikipedia.org/wiki/Iodised_salt  for more information.