Blockchain is a distributed database or digital ledger of transactions that is duplicated and shared among members of a network. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data. By design, blockchains are inherently resistant to modification of the data. The blockchain serves as an open, distributed ledger that can record transactions between parties efficiently and in a verifiable and permanent way, without the need for a central authority. This document provides an overview of blockchain technology, including its fundamentals, types, how it works, applications, advantages, and disadvantages.