I googled gopher and ground hog.
It isn't real clear, ground hog is bigger, gopher is smaller.
There are ~100 types of gophers in N. Amer.
Some are called marmots, but some groundhogs are also called marmots. Then
there's woodchucks (ground hogs) and whistlepigs (also ground hogs).
Wikipedia says groundhogs are large squirels, which doesn't make much sense.
This isn't the place for rodent identification, but, no, I didn't know the
difference between gophers and groundhogs.
Both are under ground living pests in people's yards.
I do know a prairy dog when I see one.