Understanding the term
The origins of the Bitcoin genesis block stretch back to 2009, when an anonymous developer named Satoshi Nakamoto released it. This original block contained the first 50 Bitcoins and also contained a message from the developer. Normally a block references the previous block when it is broadcasted to the blockchain.
However, the Genesis block does not have a previous block for reference. Thus, the genesis blocks of every blockchain are usually hardcoded into the software. The genesis block has a unique hash as it contains two additional leading hex zeros compared to other blocks. Satoshi Nakamoto left a message within the Bitcoin genesis block included as a time stamp. The message read “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks”.
The genesis block, also known as Block 0, is the primary block upon which additional blocks in a blockchain are added. It can thus be considered as an ancestor of every block since every new block references the one preceding it. The next block, entitled Block 1 in Bitcoin, was mined after six days.