The basic electronics on 12 volt DC to 110 volt AC inverters involves some simple Ohm's law electrical equations. The following is generalized to make it easy to understand. The power consumed by an electrical load can be considered a constant (i.e. 1200 Watts for an air conditioner). Power value is equal to voltage supplied times current drawn. Easy as PIE : Power -in Watts - is equal to Current (in amperes, expresses as I) times voltage supplied (in Volts, expressed as E).
If you have a 1200 watt air conditioner, it draws about 10 amperes of current at 110 volts. But to produce that same 1200 watts with 12 volts requires about 100 amperes of current. That is a lot, and the more amperes of current you are moving, the bigger cables you need. Curentwise, 100 amperes is the full current your trailer can pull with the standard 50 amp 2 phase RV shore power hookup.
100 amperes DC makes a good metal arc welder.
Keeping this approximate 10:1 12 volt DC to 110 Volt AC current ratio in mind is handy when working around power inverters.