El Nino is a relatively weak current that occurs annually when ocean water around the coasts of Peru and Ecuador are warmer than normal. It means "little boy" in Spanish. However, after approximately three all the way to seven years, the current lingers for an abnormally long time, which causes many usually negative changes to the atmosphere all around the world.
La Nina is the opposite of El Nino as it affects the same regions, except the waters are colder than normal. La Nina means "little girl" in Spanish. However, it only occurs about half as often as La Nino. El Nino occurs when the easterly trade winds weaken, while La Nina occurs when the easterlies strengthen. They both cause all sorts of unusual weather.
Hope this helped you.
