The blockchain is a distributed ledger, shared among all members of the bitcoin network. It is literally a “chain of blocks” and makes it possible to arrange all bitcoin transaction in chronological order. All transactions happening on the blockchain are grouped in blocks, a set of transactions. On average, a new block is added to the blockchain every 10 minutes, through the process of mining.
The main benefit a blockchain is removing any type of intermediary or trusted third party. Since all actors possess a copy of the ledger anyone can do auditing, without having to trust a third party to do so. In this way, it is always possible to be sure that all transactions are legitimate. Furthermore, the ledger cannot be manipulated, as a set of rules and incentives guarantees the cooperation between actors.