Gnosis

Gnosis is market-driven forecasting technology. It is based on proven scientific research. It has its own platform known as the Gnosis platform and you can build your own platform on top of it. It basically makes trading predictions. And correct predictions are given the tokens that were at stake for incorrect predictions. Visit https://gnosis.pm/ to access Gnosis.

The way it works is that you trade predictions or you bet on predictions. The following is the front page of Gnosis:

In the preceding screenshot, do note the question that is being asked on their home page. Will Dubai's world record for the largest New Year's Eve fireworks display get broken? You can vote yes or no, and by voting, your tokens are at stake, and an Oracle is then going to tell you whether the event happened or not. The blockchain will then check on that Oracle. Oracles are nothing but smart contracts that interact with the outside elements. They can store and retrieve data—this is just what an Ethereum transaction needs to make decisions. An Oracle is a trusted source, and after checking with this trusted source, you can determine in a blockchain whether the event really did happen or not, and you can be absolutely certain about it.

The following diagram explains exactly how this happens: