The standard map has "everything".
The roads-only maps have routing, POIs, addresses and streets.
In other words: in roads-only maps you don't see small lakes, you don't see small grass areas nor farming areas, no houses nor industrial buildups, no trees nor small bushes/forests.
There is one exception (and that's why I used small in a few of the above examples): Roads-only maps have big lakes, big forests and large "greenery" (grass, farming, etc). So only when the (multi-)polygon is large in surface area.