What is a Bitcoin block?
A batch of transactions added to Bitcoin's shared record, about every 10 minutes on average.
Miners compete to add the next block. Each block links to the one before it, which is why the record is called a blockchainBlockchainBitcoin's shared record of every payment since 2009, stored in blocks that each link to the one before — which is what makes it a chain.. Changing an old block would mean redoing all the work since.
Blocks are numbered by height, starting from 0 in 2009. Each one has room for a few thousand payments.