However the block chain can be used for more than a simple ledger. You can store code (Smart Contracts) in the blockchain.

Vitalik Buterin

A blockchain is a magic computer that anyone can upload programs to and leave the programs to self-execute, where the current and all previous states of every program are always publicly visible, and which carries a very strong cryptoeconomically secured guarantee that programs running on the chain will continue to execute in exactly the way that the blockchain protocol specifies -


A block chain is a transaction database shared by all nodes participating in a system. Block chain technology was popularised by cryptographic currency Bitcoin. Apart from financial transactions it as a number of applications. See Block Chain Projects.

Block Chain is a mechanism for trustless publication, validation and processing of instructions from simple (currency) to advanced (Cryptographic Contracts). Most well known application of Block Chain technology is Bitcoin and associated with financial transactions.