The difference between campgrounds and RV parks is self-explanatory: RV parks offer sites for RV’s. However, most campgrounds do so as well, and many RV parks also offer sites for tent campers. In this post I will use the term campground for both.
Campgrounds can be public, owned and operated by some government-controlled agency, or private. Per http://ultimatecampgrounds.com, there are about 22,500 public campgrounds in the US and Canada. I didn’t find any tally of private campgrounds on the Internet; my personal guess is at least 5 times as many.
Most public campgrounds are located in National Parks, State Parks, National Forests, in county or city recreation areas, or on open land (run by the BLM, the Bureau of Land Management). They offer all kinds of facilities for RV’s, from nothing (like in most BLM or National Forest campgrounds), to full hookups (electricity, water, and sewer) in some State Parks and a few National Parks. Although it’s hard to generalize, I would say most public campgrounds are located in more nature-related settings than the private ones, and typically the individual sites are spaced more generously from one another (I guess because they didn’t have to pay for their land like the private ones had to!). A drawback could be that public campgrounds are often located pretty far away from major thoroughfares. Roads inside the campground as well as the campsites themselves might not be spacious enough for larger RV’s, which is why we always try to check online reviews prior to selecting a public campground.
Private campgrounds are pretty much the opposite. Again by way of generalization, they are conveniently located (meaning, sometimes, right next to a noisy interstate!), can accomodate large RV’s in terms of their internal road system and site dimensions, offer hookups, and are more expensive than public campgounds in the vicinity.
Of course, there are exceptions to all of the above, so I don’t want to disencourage anyone from choosing a particular campground just because it’s private or public. The best idea is to get as much information as possible about the place you want to stay and make an educated decision.