Chad, here is a website that helps explain all the different electric configurations (especially how to wire an outlet you may install at your house), campground services, how to make and test outlets, proper wire sizing, and much more for your RV.
Just click on all the links on the left hand side of the main page, and you will learn many things. It's a great site to have bookmarked.
One of the main things to remember when using the 15 amp adapter, and you are plugged into a 15 amp outlet..............since you are now limiting your total electric usage to 15 amps, you shouldn't be using an air-conditioner, as it could require more than 15 amps to properly start.
Page 3 of the following pdf may help explain this better:
As Mike pointed out, RV's use only 120 volt, whether hooked up to a 15, 20, 30, or 50 amp supply. The 15, 20, and 30 amp supplies are always 120 volt and you will be limited to using a grand total of either 15, 20, or 30 amps worth of electrical things.
The confusing one to many people is the 50 amp supply. It is actually 240 volt, which has two 120 volt legs. Once inside a 50 amp RV, the RV's uses each one of these legs separately, so they have TWO 120 volt sides for a grand total of 100 amps.
All the electrical stuff in the 50 amp RV operates still off of 120 volts just like a 30 amp RV..............but they have 50 amps on Line 1 and another 50 amps on Line 2. (There are a few high end RV's/coaches that have 240 volt dryers, but these are the exception not the rule)
If needed, you can use the proper adapter and plug your 30 amp RV into a 50 amp campground service. The adapter is made so that it only takes one side of the 240 volts, so you will have only 120 volts feeding into your RV. You will sometimes encounter campgrounds with bad/loose 30 amp outlets, since this outlet get's used the most. There are also some campsites that may only have a 50 amp outlet, so you will need the adapter to plug your 30 amp RV into these.
WARNING: Make sure you never plug into a 240 volt 30 amp outlet, or you will fry many things in your RV. It happens more times than you think, and even some electricians wire outlets wrong when people have outlets installed at their house to plug their RV's into.
It's always a good idea to test any outlet before you plug your RV into it, to make sure it is wired correct. The first link tells you how to test outlets or you can buy surge guards that will do this for you and not allow electrical flow to your RV if something is wrong.
If you ever decide to install a 30 amp outlet at your home, make sure to use the next link as an installation guide...either for yourself or an electrician (because they do mistakenly wire it 240 volts as they don't know RV's are 120 volts)