What is the "wet foot/dry foot" policy?

What is the "wet foot/dry foot" policy?
To some, this may sound like something out of a Marx Bros. Movie, but here it goes. Current immigration laws that apply only to Cubans dictate that if an illegal immigrant (in this case somebody who braved the ocean currents by boat) makes it all the way across to American soil (the beaches of Key West, for example) then that illegal immigrant can legally stay.

If, on the other hand, he or they are caught at sea by the officials, then they are returned to Cuba. Dry foot-wet foot. Get it? Could Groucho ever come up with something so outrageous? This policy (which some claim encourages illegal Cuban immigration) was signed into law by President Lyndon B. Johnson on November 2, 1966.

What if you're an illegal immigrant from, say, El Salvador or Bolivia? You are returned to the place you came from.