Class G is "Uncontrolled Airspace." This doesn't mean it's lawless. It just means ATC does not have authority or responsibility for separation there. Where is it? Usually close to the ground (Surface to 700 (in a magenta boundary) or 1200 ft AGL) in rural areas. Why does it matter? Weather minimums are more lenient (1 mile visibility) during the day to allow work like crop dusting, but night ops require higher visibility (3 SM) because obstacle avoidance is harder.