A dApp, or decentralized application, is an application that uses a blockchain and one or more smart contracts to implement part of its functionality. In DeFi, a dApp commonly provides the user interface through which users interact with a financial protocol.

A typical dApp consists of a frontend interface and blockchain-connected logic. The frontend can be a conventional web application displaying balances, prices, liquidity, and transaction parameters. When the user performs an action, the application constructs a blockchain transaction that is then authorized through a crypto wallet.

After transaction signing, the transaction can be broadcast to the network. Blockchain nodes process it and the relevant smart contract executes the programmed logic.

A dApp can interact with several contracts in one operation. For example, a decentralized exchange interface can interact with routing contracts, liquidity pools, token contracts, and other components. One user action can therefore result in multiple contract calls within a single blockchain transaction.

The presence of a dApp interface does not automatically mean that the entire system is decentralized. The frontend may be hosted on centralized infrastructure, data may come from centralized APIs, and contract upgrades may be controlled by a limited group.

dApp risks include smart-contract vulnerabilities, malicious interfaces, phishing, incorrect token approvals, compromised wallets, and user mistakes. Users should verify contract addresses, supported networks, permissions, and the identity of the protocol before signing transactions.