One example of a cryptocurrency, bitcoin is a decentralised digital currency based on a peer-to-peer payment system built on cryptographic principles. Rather than data being stored on one central server, it is simultaneously stored on nodes in a system where each node communicates with the others to record and verify each transaction.
Information is publicly recorded in ‘blocks’. Blocks are simply collections of data and can store any type of data; bitcoin is only one of the many applications of the technology. Blocks contain not only the data that was recently stored in them, but all previous data points. This makes it possible to link one block to its previous block, creating a chain of information. This is why the underlying technology of the bitcoin system is referred to as a blockchain.