Encyclopedia Britannica, Inc.
Bitcoin relies on public key cryptography, in which users have a public key accessible to anyone and a private key known only to their computer. In a Bitcoin transaction, users receiving Bitcoins send their public keys to users transferring the Bitcoins. Users transferring the coins sign with their private keys, and the transaction is then transmitted over the Bitcoin network. So that no Bitcoin can be spent more than once at a time, the time and amount of each transaction are recorded in a ledger file that exists on every node in the network. User identities remain relatively anonymous, but anyone can see that some Bitcoins have been transferred.
Transactions are grouped into groups called blocks. Blocks are organized in a chronological sequence called a blockchain. Blocks are added to the chain using a mathematical process that makes it extremely difficult for an individual user to modify the blockchain.
(Read Mark Cuban’s Britannica essay on NFTs.)
The blockchain technology that underpins Bitcoin has attracted considerable attention, even from Bitcoin skeptics, as a basis for enabling reliable record-keeping and commerce without a central authority. Blockchain technology is also essential for NFTs (non-fungible tokens).
