campground vs camping site

campground and camping site both are nouns.

Word	Noun	Adjective	Verb	Adverb
campground	Yes	No	No	No
camping site	Yes	No	No	No

As nouns, campground and camping site are synonyms defined as:

campground and camping site: a site where people on holiday can pitch a tent

Other synonyms of campground include bivouac, camping area, camping ground, campsite, encampment.

campground (noun)	camping site (noun)
a site where people on holiday can pitch a tent	a site where people on holiday can pitch a tent