1. Canopy: This is the uppermost layer, composed of the crowns of the tallest trees. It receives the most sunlight and is home to a wide variety of birds, insects, and other animals.

2. Understory: This layer is below the canopy and includes smaller trees, shrubs, and young trees. It receives less sunlight than the canopy and is home to a different set of animals, including deer, squirrels, and snakes.

3. Forest Floor: This is the bottom layer, consisting of leaf litter, decaying wood, and soil. It is home to fungi, insects, and small mammals like mice and voles. It's also an important layer for decomposition and nutrient cycling.

While these three layers are the most common, some forests may have additional layers depending on their climate, species, and other factors. For example, some forests might have a shrub layer within the understory, or a moss layer on the forest floor.