The genesis block is almost always hard-coded into the software of applications using its blockchain. This is a special block that does not refer to the previous one. Each block created from the moment of zero can automatically track the genesis block as its ancestor through links with the previous ones.
The genesis block in bitcoin contains a hidden message in the transaction: «The Times 03/Jan/2009 Chancellor on brink of second bailout for banks» («The time is January 3, 2009, the Chancellor is on the verge of saving banks for the second time»).
This is, of course, a message from Satoshi Nakamoto, which performs two functions — it indicates the time of the creation of the first block and indicates the economic problems of the current government and the banking system.