Stick to paved, public roads and you're good to go. Your campervan is made for regular roads — not for gravel or dirt tracks, off-roading, sand, or beaches. Those are off-limits, and if you drive on them, any damage wouldn't be covered by your protection plan, so it's really not worth the risk.
One thing that catches people out: sometimes your GPS tries to send you down a shortcut that turns into a rough track, or a road that looks fine slowly turns to gravel — this happens a lot on mountain, forest, and remote coastal routes. If the paved surface runs out, don't push on. Just turn back and find another way round, even if it adds a few minutes.
The easiest way to remember it: if it's not a proper sealed road, it's not for the campervan.
Before you set off, it's also worth a quick look at where you're not allowed to travel, and at how fast you can drive once you're on the road — both are good to know so nothing catches you out along the way.