“The Optimist is a small, single-handed sailing dinghy intended for use by children up to the age of 15. Nowadays boats are usually made of fiber reinforced plastic, although wooden boats are still built.
It is one of the most popular sailing dinghies in the world, with over 130,000 boats officially registered with the class and many more built but never registered.
The Optimist is recognized as an International Class by the International Sailing Federation.”
“…The International Optimist is sailed in over 100 countries by over 160,000 skippers and it is the only yacht approved by the International Sailing Federation exclusively for sailors under 16. At the Beijing Olympics, 85% of medal winning skippers were former Optimist dinghy sailors.”
Read much more in the Wikipedia article on the Optimist sailboat.