Gnosis (GNO) is a cryptocurrency made by Martin Koppelmann and Stefan George in 2015. It is a decentralized, open-source prediction market protocol that is built on top of Ethereum.

Gnosis was one of the 1st major decentralized applications (dApps) to launch on Ethereum in August 2015. It allows users to create arbitrary events to make predictions on future outcomes. If the outcome matches the prediction, the participants receive a certain profit from the invested funds within that prediction. Conversely, users who predicted the wrong outcome will lose their invested funds - thus creating a decentralized prediction market. 

The Gnosis platform is built with 3 layers, the first being Gnosis Core which provides the foundational smart contracts for the Gnosis prediction market (and other applications) to use. It allows for the use of basic functions such as regulating the issue of tokens and is also responsible for the platform's interface. Furthermore, the core also allows users to conduct fast transactions with no fees.

The second layer is known as the Service layer and this is designed to host the user experience tools such as chatbots, stablecoins, and oracles. Decentralized oracles help to gain data from outside networks and plug them into the prediction markets for the outcomes. The final layer is known as the application layer and this is design to host the front-end dApps solutions built on the Gnosis blockchain. These dApps will mainly be created by 3rd-party developers and may charge a fee. Some applications already launched include a decentralized dutch exchange called DutchX and the Gnosis Safe wallet solution.