Salt is 100% NaCl (sodium chloride) (er, plus trace gunk, like iodine).

Lite-salt is 50% NaCl and 50% KCl (potassium chloride).

No-salt is 100% KCl.

Lite salt is traditionally suggested for folks who need to cut their
sodium intake, but LCers find it suggested for folks to need to boost
their potassium intake.  Morton Lite-salt also includes traces of
calcium and magnesium salts.  The extra minerals in lite salt help
with muscle cramps common among LCers due to the diuretic nature of
LCing.

This description is from the Morton web site (they make Lite Salt)

http://www.mortonsalt.com/consumer/products/foodsalts/litesalt.htm

A salt and potassium chloride mixture* with iodide and a freeflowing
agent, contains 50% less sodium than regular salt. Use for baking,
cooking and at-the-table seasoning just like regular salt, for the same
great results.

Sold in an 11-ounce light blue shaker.

*Should not be used by persons on a sodium or potassium restricted diet
unless approved by a physician.

Regular salt is just salt (with maybe some iodine and anti-caking agents).
Lite salt is salt mixed with a salt substitute, usually potassium chloride.