A value describing the number of blocks preceding a given block in the blockchain.
Every blockchain is made up of a series of blocks, organized sequentially. Each block stores information about transactions that were conducted on the blockchain during a given time period. Blocks are added to the end of the blockchain at given intervals.
The block height, therefore, is a measure of the number of blocks that have been created on the blockchain prior to the block in question. It could also be thought of as b-1, where b equals the total length of the blockchain.
Every block in the blockchain has an associated block height value. The first block in the blockchain, known as the genesis block, has a block height of zero, reflecting the fact that there are no blocks before it in the chain.
Block height is an important measure of the rate at which new blocks are being added to the blockchain in question. It is also used as an identifier for each individual block.
However, in some circumstances, two blocks might have the same block height. Blocks are created when a cryptographic problem is solved by a miner or group of miners. So, if the same problem is solved simultaneously by more than one party, two blocks will be created with the same block height. This may precipitate a fork, or it may result in a block being orphaned. Whichever outcome occurs, duplicate blocks cannot appear on any one given blockchain.
Block height is one of the key pieces of information displayed on block explorers. It is also one of the most useful pieces of information for users wishing to find details of specific blocks or transactions using an explorer.