That's correct!

Expos (World's Fairs) have been held for quite a while - http://en.wikipedia.org/wiki/List_of_world%27s_fairs. In recent years a bit more structure has been added to the hosting process. Recognized Expos are now held only once every 2-3 years. Those are broken into 2 categories. Universal Expositions (very large, open for 6 months), like the one in Shanghai, are held on years ending in 0 and 5. International Expositions (smaller scale, open for 3 months), like this year's expo are held once in a year ending in 2/3 or 7/8, between two Universal Expos

Shanghai's Expo 2010 was the highest attended expo in history, with something like 70 million visitors. I was dying to visit but I was starting a new job that required me to be in India for 3 months during that time and I couldn't make the trip.

At least 106 countries have confirmed their participation in this year's expo, whose theme is "The Living Ocean and Coast". The last projection I heard was for 8 million visitors


Expomuseum.com is a great resource for more information