Tendermint Core is a blockchain consensus engine that enables secure and efficient decentralized applications. It combines a Byzantine Fault Tolerant (BFT) consensus algorithm with a networking layer, allowing nodes to agree on the state of the blockchain even in the presence of faulty or malicious actors. This technology is designed to provide fast finality, meaning transactions are confirmed quickly and cannot be reversed. Tendermint Core is often used in conjunction with the Cosmos ecosystem, facilitating interoperability between different blockchains and enhancing scalability for decentralized applications.