Blockchain app development involves creating decentralized applications (DApps) that utilize blockchain's secure and transparent nature. Developers code smart contracts, self-executing agreements with predefined conditions, enabling trustless interactions. Blockchain apps find use in various domains like finance, supply chain, and more, ensuring data immutability and reducing intermediaries. Ethereum, Binance Smart Chain, and other platforms offer tools for building these apps. Successful development demands proficiency in blockchain protocols, programming languages, and a deep understanding of the decentralized ecosystem.