Bitcoin’s purpose is to establish trust and allow transactions across a global ledger, specifically with no need for a third party. Trust is created through peer-to-peer collaboration and cryptography rather than a singular authority figure. Every transaction is shared across millions of computers.
Blocks are calculated and mined every 10 minutes with an updated list of transactions. These are linked together to form a chain of time-stamped blocks that represent the whole history of the blockchain. This is a clever tactic against hackers, who would have to compromise every computer on the blockchain using high levels of cryptography while everyone is watching.