All cryptocurrencies are blockchains but not all blockchains have to be used to keep track of monetary transactions.

To be a blockchain, each unit of data must reference the previous unit and contain a timestamp. By linking each record to the ones that have come before it the user can reasonably expect that the information in the past has not been altered - that is, that it is an accurate representation of the state of the system preserved throughout time.

Most blockchains are run as a public Peer-to-Peer network on open-source software. Each node has a copy of the distributed ledger. This decentralized trust model is less efficient than a central ledger that a bank might operate but not having to trust any one entity is a highly desirable feature.

While private blockchains have been proposed for use in business, none has been found to be viable as applications that do not require permissionless trust become needlessly less efficient.

Any given chain is only as secure as the difficulty of altering the chain maliciously. People value Bitcoin because it is a ledger of transactions that cannot be altered without great expenditure of energy.  

Ironically, the open nature of the bitcoin network allows blockchain analysis companies to view the behavior of individuals by following patterns in the chain.

Wasabi Wallet CoinJoin technology is critical to maintaining the permissionless usability of the bitcoin network.