Returns the number of blocks in the longest blockchain, starting from the genesis block (height 0)

How is this used?

You're climbing a mountain and want to know exactly how high you've climbed from sea level to gauge your progress. In the Bitcoin blockchain, the 'getblockcount' command provides a similar measure, telling you how many blocks have been added to the blockchain since the very first block, known as the genesis block. This count gives you a clear idea of the length of the blockchain, which is a direct indicator of its growth and activity over time.