The term ‘blockchain’ is a reference to a constantly growing, digital list of records, termed ‘blocks,’ which are secured and connected to each other, through the use of cryptography. Cryptography – the namesake of cryptocurrency – is the science of digitally encrypting information in such a manner that would make it impossible for unauthorized parties to access or alter it in any way. It is the application of cryptography that makes information stored in blocks secure and reliable. These digital blocks of data come together to form an electronic database, which is essentially a publicly accessible (i.e. decentralized) ledger.
Decentralisation, is in fact, a key aspect of how the blockchain functions and keeps itself immutable – secure and free of malicious interference. In a decentralized network, information is not locked up in a central server, since there simply isn’t one. Instead, it is stored in the computers of all the participants of a given network. Every participant (or peer) has access to the ledger, that records and maintains the complete history of all transactions and can be referenced to check if a potential transaction is legitimate or not. Due to these factors, any sort of unauthorized transaction could not take place by definition, as in order for any transaction to proceed, it would require all the peers in the network to review (and subsequently approve) it before it could take place.