The common assumption that Bitcoins are stored in a wallet is technically incorrect. Bitcoins are not stored anywhere. Bitcoin balances are kept using public and private “keys,” which are long strings of numbers and letters linked through the mathematical encryption algorithm that was used to create them. The public key (comparable to an international bank account number or IBAN) serves as the address published to the world, and to which others may send Bitcoins.
^ Jump up to: a b c d "Statement of Jennifer Shasky Calvery, Director Financial Crimes Enforcement Network United States Department of the Treasury Before the United States Senate Committee on Banking, Housing, and Urban Affairs Subcommittee on National Security and International Trade and Finance Subcommittee on Economic Policy" (PDF). Financial Crimes Enforcement Network. 19 November 2013. Archived (PDF) from the original on 9 October 2016. Retrieved 1 June 2014.
Health care providers can leverage blockchain to securely store their patients’ medical records. When a medical record is generated and signed, it can be written into the blockchain, which provides patients with the proof and confidence that the record cannot be changed. These personal health records could be encoded and stored on the blockchain with a private key, so that they are only accessible by certain individuals, thereby ensuring privacy

Blockchain is the digital and decentralized ledger that records all transactions. Every time someone buys digital coins on a decentralized exchange, sells coins, transfers coins, or buys a good or service with virtual coins, a ledger records that transaction, often in an encrypted fashion, to protect it from cybercriminals. These transactions are also recorded and processed without a third-party provider, which is usually a bank.
Getting Bitcoin blockchain explained is essential to understanding how blockchain works. The Bitcoin blockchain is a database (known as a “ledger”) that consists only of Bitcoin transaction records. There is no central location that holds the database, instead it is shared across a huge network of computers. So, for new transactions to be added to the database, the nodes must agree that the transaction is real and valid.
On 3 January 2009, the bitcoin network was created when Nakamoto mined the first block of the chain, known as the genesis block.[19][20] Embedded in the coinbase of this block was the following text: "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks."[10] This note has been interpreted as both a timestamp and a comment on the instability caused by fractional-reserve banking.[21]:18