Confirmation

A block is a batch of Bitcoin transactions added to the chain about every ten minutes. The miner who finds it collects the new coins and the fees.

The blockchain is Bitcoin's shared history of payments: a chain of blocks where each block points to the one before it. Changing an old block would break every link after it.

The mempool is the waiting room for Bitcoin payments: transactions sent but not yet in a block. Miners usually pick the ones paying the highest fee per byte first.