Forests can often be found very close to Woodlands, where the initial spawn-points of player-characters are located.
Forests typically consist of rather high hills (different from the more open Woodlands on rolling hills). The ground of Forests is mostly covered with green Grass and some patches of Tallgrass on them.
Medium-sized to large trees will grow all over the place closer to each other than in Woodlands; mostly Cragwood-trees, birch-like Ashenwood-trees and also several Autumnwood-trees with colorful foliage that come in three different colors (yellow-brown, reddish-brown and red), also some pine-like Elderwood-trees here and there, often on brown Dead Grass with Rimecones underneath at the borders of Forests.
Several Caves can be found at the feet of hills and/or at the base of large trees and such can be easy to overlook. Caution should be exercised or a heavy fall into hostile darkness might occur! Small lakes can only rarely be discovered in Forests, and rivers are also rare. Cragwood Logs can be often seen lying on the forest ground though, even in areas where other types of trees are the dominant species.
Below the thin layer of grass there's usually Dirt that is forming the hills, then Stone and further down the Fossil layer begins, where Caves will often lead into. Dirt that is placed on the surface and touches green Grass will turn into Grass after a short while (as long as player-characters are nearby). Dirt will not turn into Dead Grass though, neither will green Grass decay into Dead Grass.
Tallgrass (providing you with Wheat-seeds randomly) can grow on Grass occasionally, as well as patches of 5 Red Mushrooms each. These mushrooms will even regrow - very slowly - in time. Brown Mushrooms can be found embedded in Dirt right under the thin layer of Grass; and at cave-entries.
Yellow Flowers are hidden in a quite large amount amongst the leaves of Cragwood-trees, as well as Autumnwood Flowers on Autumnwood-trees of course, Red Flowers on the birch-like Ashenwood-trees and Blue Flowers on pine-like Ashenwood-trees. Vines will often cover the larger Cragwood-tree-specimens and Moss can often be found on Ashenwood, while Beeswax forming hives can be discovered on many tree-tops amidst the leaves.
Forests are peaceful biomes during the (ingame-)day. Leafies are the most common inhabitant of Forests, and also Autumn Leafies will gather under Autumnwood-trees. Additionally to them, yellow Pigsies will often spawn on Grass, and perhaps a rare Chizzard here or there.
At night Night Pigsies will pop up on the Grass in darkness, also Night Leafies on the ground as well as on top of trees. Night Rocksters and Night Pigsies might come out of Caves additionally; occasionally even Mirus. Of course creatures from nearby biomes might intrude into Forest-biomes as well.
Wood Treasure Chests can occasionally show up during (ingame-)night-times in dark places in range of view of player-characters in this biome. These valuable findings can also spawn on tree-tops and at cave-entries.