An RV park is catered to those with RV's, therefore the sites will have electric, water, sewer, and maybe cable TV. There is usually a pool and game room, and many other activities (think "resort"). A campground may contain RV's, may have water, electric, and sewer, but you will see plenty of people in tents. The activities are more of ones that you will entertain yourself with - hiking, biking, fishing, etc. Some RV Parks will allow tents, some may be so restrictive as to only allow Class A RV's. I've never seen a campground that wouldn't allow people under the age of 55, but I have seen RV parks that will say "Adult only".
I suppose they could. I've seen some where I would have to say no, because most of the site is asphalt, and they won't allow a fire. I've also seen some where I would say yes, as they have soil and grass at each site, shady trees, and allow fires.
In my opinion, nothing beats a state or federal campground, and that is where I do almost 100% of my RV'ing. Others will prefer the resort type.
Up here we hav Provincial parks parks which are private mostly but I haven't been to one yet that had grass. No wait just 1 Eral Rowe. Mostly gravel or dirt. We like to stay in some of the Private parks "RV Parks" which are owned and operated by private owners. They're geared mostly towards kids with tractor rides swimming pool mini golf and other activities that the kids love to do. the sites are open and not to private for the most part but sometimes you get lucky and get a priviate spot. Depends where you go.