A blockchain is a shared ledger that stores information about transactions in a distributed manner.These transactions are carried out between people within the blockchain, which is formed by the computers of its participants. These computers provide the computing power to continuously maintain the blockchain by performing calculations and validating transactions.These computers are called nodes, and each node on the network owns a complete copy of the blockchain.That is, when you need to validate a transaction, you connect to the bitcoin node set to make sure the transaction is valid for each node. When you use a bitcoin wallet, that wallet will connect to full nodes to see the blockchain.