Blockchain is a database that contains linked blocks of transactions. Each block contains a list of transaction hashes and details like the sender and receiver. Transactions are ordered into blocks in a highly secure manner through cryptography. While private blockchains within companies are more like databases, public blockchains provide security through decentralization and incentives that prevent attacks by any single party controlling over 51% of the network. However, blockchain technology also faces challenges in scalability and adoption that will take continued development to fully address.