What is a Jeopardy playing supercomputer?

After pretty much solving chess with Deep Blue, IBM is building a computer called Watson to beat human opponents at Jeopardy. It's not quite at Ken Jennings' level, but it's holding its own versus lesser humans.

Deep Blue was able to play chess well because the game is perfectly logical, with fairly simple rules; it can be reduced easily to math, which computers handle superbly. But the rules of language are much trickier. At the time, the very best question-answering systems -- some created by software firms, some by university researchers -- could sort through news articles on their own and answer questions about the content, but they understood only questions stated in very simple language ("What is the capital of Russia?"); in government-run competitions, the top systems answered correctly only about 70 percent of the time, and many were far worse. "Jeopardy!" with its witty, punning questions, seemed beyond their capabilities. What's more, winning on "Jeopardy!" requires finding an answer in a few seconds. The top question-answering machines often spent longer, even entire minutes, doing the same thing.