Also, kosher salt should have no additives. That is, sodium chloride and nothing else. Differents brands of kosher salt will have different sized grains of salt. Diamond Crystal has a larger grain or flake than Morton's.
Table salt has additives such as iodine compounds and other salts to promote free flowing.
Sea salts also contain other salts and minerals common to the seawater it is taken from. When the seawater is evaporated, these other ingredients remain and contribute to the different colors and flavors of sea salts.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan