DApp is an abbreviated form for Decentralized Application. DApps run on decentralized public blockchains like Ethereum. The main difference between DApps and apps is that DApps are engineered to be governed by their code, with no human intervention from the moment they are launched. The term decentralized means that there is no single point of control, it is peer controlled and entirely run by the code.
DApps are usually entirely or partially based on open-source code, providing transparency.
2key Network is a DApp running smart contracts on the Ethereum network that governs its behavior, is decentralized, and mostly open-source.