The dark forest, formerly and also referred in Bedrock Edition as the roofed forest is a biome which contains many trees, close together, with a thick canopy, making it significantly darker than other forests at ground-level.
Like a regular forest biome, the dark forest holds some useful resources for players. Most obvious is the abundance of dark oak trees, which can be harvested for wood. However, because of the low amount of light penetrating the thicker-than-usual forest canopy, it is common to find hostile mobs in the shade of the trees, even during daytime. This can make exploration in a dark forest dangerous for a player. Most passive animal species can be found here, as well as flowers (necessary for making dyes), mushrooms (both small and giant), and grass (useful for gathering seeds). Woodland mansions may rarely be found within this biome.
The roofed forest biome is packed so tightly with trees that almost no light can break through the thick canopy of leaves. This presents a beautiful home for your deadliest enemy mobs, spawning and attacking in the shadows of the leaves. Players should keep watch for monsters as they collect logs, as monsters will more often spawn in the low light levels of thick tree leaves; but logging the outer trees of the forest, situated within range of sunlight, is a great, safe alternative, as the trees contain a lot of wood, and it would be efficient to mine them without worrying about monsters. An interesting idea is to build a treehouse atop the thick canopy, as the leaves provide a safe way to travel in daylight hours (just don't drop through a hole between 2 trees - you'll end up in a deadly situation if you lack equipment.) Forest fires are also very dangerous, because most of the trees are conected.