What is Prediction Market?

Legal Definition
Prediction markets (also known as predictive markets, information markets, decision markets, idea futures, event derivatives, or virtual markets) are exchange-traded markets created for the purpose of trading the outcome of events. The market prices can indicate what the crowd thinks the probability of the event is. A prediction market contract trades between 0 and 100%. It is a binary option that will expire at the price of 0 or 100%.

Research has suggested that prediction markets are at least as accurate as other institutions predicting the same events with a similar pool of participants.
-- Wikipedia
Legal Definition
An economical market based around an activity, or likelihood. For instance, presidential elections. The public will purchase or sell as per the likelihood of the event.