The genesis block is the very first block in a blockchain. It serves as the foundation of the entire blockchain system. In the case of Bitcoin and many other cryptocurrencies, the genesis block contains the first transactions ever processed and starts the blockchain. This block is hard-coded into the software of the applications that utilize its blockchain and, as such, is unique because it does not reference a previous block. The genesis block often holds historical significance and can include unique messages left by the blockchain's creator. For a detailed explanation of the genesis block and its role in blockchain technology, you might find this article helpful:
https://paybis.com/blog/glossary/what-is-the-genesis-block/ It provides insights into the origin and importance of the genesis block in initiating and legitimizing a new blockchain.