After reading parts 1 & 2, you now hopefully have a comprehensive understanding about the laws and how to get started.
Once you've chosen your first gun, you should try to understand how to operate it. In regards to the aforementioned G&G combat machine, it runs off an electric battery operated system. This means you will need a battery to get the gun to fire. With a gun like this, it's best to buy a 8.4v NiMH battery as they are versatile, cheap and the chargers can also be purchased at a low cost!
In regards to charging, every battery is different. For example: an 8.4v 1600 MaH NiMH type of battery on a standard charger should charge for 8 hours on its first charge, and then 5 hours every time after. You should be careful when dealing with batteries, because even though the NiMH batteries are one of the safest kinds out there, they still need to be treated with caution. Make sure they don't get dropped onto any sharp objects, and take great care when you handle them! With almost everything to do with airsoft, please do keep them out of reach from children as they are quite powerful. Avoid over-charging batteries, if your battery starts to become hot or even mildly warm, turn the charger off and let it cool. When batteries heat on charge, it usually means they are at their full capacity. If it is very hot to the touch we recommend disposing of the battery because this is not safe or usual battery behaviour.
Gas power comes in a few different forms, but the main three used in Airsoft are: Green Gas, C02 and HPA. Green gas comes in a bottle which you then fill up a mag from, C02 are small metal cylinders which you insert into a mag in full, and HPA is a tank which leads to your gun which will feed your gun gas as you fire (though I wouldn't worry about this until you get more into the sport!).
Finally spring power is most commonly used in very basic airsoft guns or Airsoft Snipers. Usually you simply pull back a bolt which charges a spring then pull the trigger to let the spring forward.