Gas is a resource that's produced in a Gas Plant and considered the second most important resource in Galaxy at War Online.
Gas is needed to fuel ships of all kinds and in certain cases are required to unlock levels of researches, gas can also reduce flight times by 20%.
Fusion Reactors require gas to function and colonizing planets with low temperature can increase the yield of gas from Gas Plant but also increases gas cost of Fusion Reactor.
Sending a fleet anywhere will cost a specific amount of gas and if returning the fleet before arrival (at any time) will not give back this amount of gas, not even partly. For this reason be extra careful when sending a fuel intense fleet somewhere.