Blockchain is the technology that underpins all cryptocurrency systems and networks. It is a type of distributed ledger for maintaining a permanent and tamper-proof record of transactional data. A blockchain functions as a decentralized database that is managed by computers belonging to a peer-to-peer (P2P) network. Each of the computers in the distributed network maintains a copy of the ledger to prevent a single point of failure (SPOF) and all copies are updated and validated simultaneously. Some blockchains are publicly available, like Bitcoin, while others are private and cannot be viewed outside the system, like XRP.