Difference between Hurricane, Cyclone and Tornado

As hurricane Ike and hurricane Gustav leading to large scale devastation in United States of America, I have often wondered why some parts of World do not have these violent high pressure events.

May be someone could tell me that. I also live along the ocean coast lines but I have never heard of hurricane . A couple of days ago, I heard weatherman refer to certain kind of hurricane as cyclone. I was totally surprised as I always believed that hurricane and cyclone is the different thing. This added to my curiosity and decided to conduct a research in order to get an answer for my question. I decided to do a conduct a research on this matter. The answer that I got left me flabbergasted. I came to know that hurricane, cyclone and tornado are one and the same thing.
If a storm is formed in the Atlantic or eastern Pacific Ocean then it is known as hurricane. Every storm that endangers the United States is a hurricane. Cyclones are the storms that originate in the Southern Pacific. Generally they are not prevalent as hurricanes because of the cold water temperatures. Tornadoes often occur in the northern hemisphere. A tornado is generally small in diameter and rapidly rotating winds form a vortex that is accompanied with a thunderstorm that could be quite devastating. A tornado is also known by the name twister. Tornadoes are very difficult to study and predict.
It does not matter what we called them. These three are all dangerous storms that can be quite devastating on their day.