Blocks

In Chapter 3, Blockchain 101 - Assets, Transactions, and Hashes, I explained that when assets are transferred from one entity to another, they are recorded as a transaction. A blockchain sees a great deal of transaction activity, so instead of recording every transaction separately, the transactions executed during a given period of time are permanently recorded in a block. Each block is made up of a list of transactions. Think of it as a paper ledger or notebook where an individual page holds multiple records. In this case, each page represents a block.

How many transactions each block can hold depends on the configured block size of the blockchain and the payload size of the combined transactions. It does not mean that a block always has to reach its maximum block size in order to be verified, as a block can also hold as little as one transaction. In essence, a block records some or all of the most recent transactions that have not yet been processed, as shown in the following diagram: