Block
Blocks are files where data pertaining to the blockchain network are permanently recorded. A block records some or all of the most recent blockchain transactions that have not yet entered any prior blocks. Thus, a block is like a page of a ledger or record book. Each time a block is ‘completed’, it gives way to the next block in the blockchain. A block is thus a permanent store of records which, once written, cannot be altered or removed.[2]
Transaction data is permanently recorded in files called blocks. They can be thought of as the individual pages of a city recorder's recordbook (where changes to title to real estate are recorded) or a stock transaction ledger. Blocks are organized into a linear sequence over time (also known as the block chain). New transactions are constantly being processed by miners into new blocks which are added to the end of the chain.[3]
Blocks are usually 1mb. Assuming an average transaction occupies 570 bytes of data, then a block can contain approximately 3,500 transactions, given the 1 MB limit.[4]