The most elementary definition of blockchain is a common, digitized ledger that may not be altered after a trade was recorded and verified. All parties to this trade, as well as a significant number of 3rd parties maintain a copy of the ledger (i.e. the blockchain), which means it would be nearly impossible to amend every copy of the ledger globally to fake a trade.
Bitcoin's success has triggered the institution of nearly 1000 new cryptocurrencies, leading to the delusion that the sole use of blockchain technology is for the production of cryptocurrency.
However, the blockchain technology is capable of a good deal more than simply cryptocurrency creation and may encourage such matters as trades that require personal identification, peer evaluation, elections and other kinds of democratic decision-making and audit trails.