VERY briefly...
...how do I find out if it has a gray and black water tank.
Other than models designed for permanent set-up in a trailer park, they all do. If the waste water from sinks, shower & toilet doesn't run out on the ground and doesn't back up inside on the first use, you have the tanks. The gray water tank catches waste from sinks & shower, while the black tank catches toilet waste. Occasionally a bathroom sink will also dump into the black, but that's incidental in the big scheme. You will have two pull handles on the lower side (usually left) that open to drain the tanks into an external sewer. One will be in a 1.5" pipe - that's the gray waste. The 3" pipe is the black. Typically those two share one physical outlet.
The electrical system is a dual one, 120vac like a house and 12dc like a car. The lighting, water pump and all the control circuits for appliances are powered by 12v, while regular wall outlets have 120v power. You only have 120v when connected to shore power or a generator. The 12v system has a battery and also a 12v converter that makes 121v from 120v when you have shore power available. The converter also includes a battery charger to recharge the battery as needed.
You have a fresh water tank with a water pump to supply water inside the trailer, but it can also use water from an external source ("city" water). City water is delivered by a hose from an external spigot.
That should generate a few hundred other questions, so I'll leave it at that for now.
There is a ton of beginner info on YouTube - suggest you do some viewing there. You can also Google "RV 101" and find lots of beginner tutorials.
