A good intro, I always think of the sun when figuring out my AC cable, black gets hot in the sun the grass grows green on the ground and the white doesnt care or stays neutral.
When choosing wire size, don't just consider volts and amps - distance also matters. The further the distance (from battery/source to the load - ROUND TRIP), the larger the wire size too. Say if, for example, 14GA wire was sufficient for a 2ft run, a 10GA wire would be needed for the same amperage if it were a 15ft run. There are many charts available online to describe your particular given situation.
