Most TT work like this:
You have both 12V and 110 AC power. There is an inverter/control panel that controls the various elements in the camper.
Things like lights, automatic lighting of propane appliances, water pump, etc (basically your essentials) run off 12 V power. That power is supplied by an onboard RV/Marine type battery. That battery is charged in two ways - either by the power cord when plugged into 'shore' power 110 outlet, OR (slowly...) by the tow vehicle. Some folks do mods to their TT to add a 2nd battery, or solar panel for recharging 12V which gives you more time 'off grid' or 'boondocking', also called 'dry' camping where you are parked somewhere you don't have a shore power outlet availalbe to plug into.
You don't want to park the Tow Vehicle (TV) with the engine OFF and your TT connected, as if you have anything running in the TT (like the fridge) that uses 12V it will drain down your vehicle battery. If you are parking for any length of time, unplug the power cable from the TV.
When you are at a campsite, there is a power cord to connect your RV to the shore power outlet at the campsite. This supplies 110 AC to the camper. That allows you to run the other features of the camper - things like Air conditioning, microwave and 110 outlets. It also charges the battery and the converter in the unit will run the 12V stuff off the 110 shore power.
Most TTs have 30amp connector. You can purchase an adapter that allows you to plug into a standard wall outlet BUT you won't be able to run your Air Conditioner and maybe microwave unless you have a full 30 amps (it will usually trip a breaker either in the house where you are plugged in, or in the camper). However you can leave it plugged in like that when at home to keep your battery topped up.
Some larger units and motor homes use 50Amp/double pole service. Again, there are adapters to step that down to 30Amp and 20amp if you are camping somewhere there is no 50 amp service.
Most ALL commercial campgrounds and most public park type places will at least have 30 amp service available.
Propane tanks are used to supply fuel for cooking (stove/oven) and heating, and also can be used to run fridges when not on shore power.
Refrigerators - most RV fridges run either dual or triple power, meaning that they will run EITHER on propane OR 110 (and most auto-switch between, defaulting to 110 when available) OR some are triple power and can run off 110, propane OR the 12V battery (but bad idea to run off battery unless you are hooked up to tow vehicle, as it's a big hog and will drain your battery pretty quickly)
Water heater: Either it's propane only (with or without electric auto-light, depending on model, OR some have 110/propane where it will default to 110 when available to save your propane.
Furnace/Heat: depends on the model, but most larger TT's have furnace that autolights and runs off propane
AirConditioner: a real power hog - ONLY works when plugged into shore power
Microwave: same as A/C unit - only works when on 110
Lights & water pump: run off 12V so you can use these when dry camping/no hookups
Other stuff like power lifts on popups and power stablizer/tongue jacks, slide out motors etc usually run off 12 V so they work when not on shore power. There is a manual crank provided in case of dead battery so you can always manually extend/retract slides and jacks if you have to.
As far as the other main system - plumbing... depends on the model, but the standard setup is a fresh water tank for holding fresh water, with a water pump used to pressurize the faucets. Most RVs also have a 'city water' port where you can plug in a water hose from a faucet at the campsite, which bypasses the water tank completely. *ALWAYS use ONLY the special white RV water hoses to fill the tank or hook up to city water *
Sewage is usually two tanks. Waste water from sinks/shower is stored in the 'grey' tank and the toilet empties into the 'black' tank. Those tanks are dumped into a sewage system either at a specific dump site OR at the campsite if sewage hookups are provided. There are tons of other threads about proper maintenance and care of sewage system.
Some smaller popups do not have a toilet/shower. Some others have a toilet, but it's a 'cassette' toilet, meaning that there is no black tank underneath the trailer and the waste is stored inside the toilet in a cassette that must be removed and emptied as needed.
Most all RVs at least have a sink for food prep/hand washing.
I think that's the basics.
2012 Flagstaff V-lite 30 WTBS
2011 Ford Expedition
4 kids and a hubby & never enough time to camp!
2011: 17 nights 2012: 26 nights 2013: 46 2014: 20 2015: 16