A blockchain is made up of blocks. One block builds on top of the previous one. You can imagine this as either a chain or as a building of blocks. Either way, block height refers to how many blocks there have been in the chain so far.

The genesis block is the very first block in a blockchain. It’s block height would be zero. After that the number is always a positive integer greater than zero.

What’s in each block? Imagine Alice sends 1 bitcoin to Bob. These are transactions and they get bundled together and referred to as a block. As well as containing a batch of transactions, each block has cryptographic hash and time stamps.

Several different cryptocurrencies use blockchains. The Bitcoin protocol has a block generation time of roughly 10 minutes (though other chains have different times). Simply put, this means a new block is added to the Bitcoin blockchain at an approximate rate of 1 block every 10 minutes for as long as the Bitcoin blockchain is running -- which could be for hundreds of years or even forever!

So when someone tells you a block height number, what they’re saying is the number of blocks in the chain and the very first block in the blockchain.

Such technology helps in creating permanent, secure digital recordings. And this can be used for more than Bitcoin and cryptocurrencies. These blocks are essentially data units and can thus store all kinds of transactional information on the network -- such as smart contracts on the Ethereum network.

You can check what the current block height is of any blockchain network with a simple Google search.