Block number refers to the unique identifier assigned to each block in a blockchain. As transactions occur, they are grouped into blocks, which are then added in a linear, chronological order to the blockchain. Each block is linked to the one before it, forming a secure chain of data.

The block number starts at zero for the first block, known as the genesis block, and increments sequentially as new blocks are added. This numbering allows users to easily reference specific blocks and helps maintain the integrity of the blockchain. Block numbers play a critical role in ensuring transparency and traceability.

By knowing the block number, anyone can verify the history of transactions, track when they were processed, and validate the current state of the blockchain. In summary, the block number is a fundamental aspect of blockchain technology that aids in organizing and securing transaction data. It enables users to navigate the blockchain efficiently while supporting overall system reliability.