GAS is the operational token that powers the smart contracts and tokens built on the NEO blockchain. 
Neo’s alternate token, GAS, is generated at a rate of 8 GAS per block with the construction of the blockchain. The rate of production is reduced by 1 token for every 2 million blocks generated. Sometime around 2039, GAS circulation will reach 100 million and production will cease. Unlike NEO, GAS can be divided.
GAS dividends also accumulate as fees to the network. Users pay in GAS to deploy and run smart contracts. Fees are proportional to the computing resources consumed by the contract. These fees are distributed to ‘bookkeepers’ as reward for their activity on the network