Block is a fundamental unit of blockchain technology, containing a set of verified transactions linked in a secure, immutable chain. Each block is cryptographically connected to the previous one, ensuring transparency, decentralization, and data integrity. Blocks play a crucial role in Bitcoin, Ethereum, and other blockchain networks, enabling secure peer-to-peer transactions. As blockchain adoption expands, innovations like sharding and rollups aim to enhance block processing, scalability, and efficiency for Web3 applications.