What is involved in creating a genesis block? What makes it different from the other blocks in the chain.
There is only one (Bitcoin) chain, and the Genesis Block is the first block in that chain.
This block was created by Satoshi Nakamoto as the first link in the blockchain. It is hard-coded into the refernce Bitcoin client. To create it, it was "mined" like every other block, except it was at the minimum difficulty level, and contained arbitrary data.
The following quote from The Financial Times is embedded in the block's binary data
The Times 03/Jan/2009 Chancellor on brink of second bailout for banks
This serves to prove it was generated on or after January 3rd 2009, as well as a political statement regarding the global economy.
The genesis block is really nothing more than a block that doesn't have a previous block. Creating a new genesis block only involves setting the
previous hash part of the block to all zeroes. Because it doesn't have a previous block, it's automatically the first block in the chain, and creating a new genesis block means that you create a new block chain.
There are actually four 'official' genesis blocks out there, one for the main Bitcoin chain, and there have been three 'test nets' so far. But there's nothing stopping you from creating your own genesis block (although it's pretty pointless).