Gas is the cost that the Ethereum network charges to process a transaction. It is a method to measure computational steps necessary for a transaction on the Ethereum network that then translates to a fee for network users. More intensive actions require more gas and this acts as an anti-spam measure to ensure the network is not clogged.

Genesis Block
Is the name of the first block of Bitcoin ever mined or the very first block in a block chain. The genesis block of Bitcoin was created on January 3, 2009 when it marked the birth of the Bitcoin blockchain. On the Bitcoin genesis block quotes the headline of the New York Times the day it was created: “03 / Jan / 2009 Chancellor on brink of second bailout for banks”, indicating the intent behind what Satoshi Nakamoto had just created.