A blockchain consists of blocks that are stacked on top of each other, forming a chain. The block height represents the number of blocks in the chain. The first block, called the genesis block, has a block height of zero, while subsequent blocks have positive integer heights.
Each block contains a batch of transactions, like when Alice sends 1 bitcoin to Bob. Along with transactions, blocks include cryptographic hash and timestamps.
Various cryptocurrencies use blockchains. For example, in the Bitcoin protocol, a new block is added approximately every 10 minutes. The block height indicates the number of blocks in the blockchain since the genesis block.
Blockchain technology enables the creation of secure and permanent digital records. It extends beyond cryptocurrencies and can store various transactional information, such as smart contracts on the Ethereum network.
You can easily find the current block height of any blockchain network through a simple Google search.