What is the significance of the forest?

The use of the forest as a dangerous setting for man's moral welfare is common in the writings of the early Church Fathers, such as Augustine of Hippo (354-430 CE), who notes in In Ioannem "this forest [is] so immense and full of snares and dangers." For Christian writers, the forest often becomes a metaphor for Hell or, more correctly, the absence of God. Just as a forest, dense with trees, obscures what lies before the wanderer, Dante's own moral compass spins wildly, leading the him deeper into a confused state. As many commentators on Dante's journey into the forest have noted, the forest mirrors the state of Dante's soul--lacking the light of truth and seeking the light in the wrong place.
https://www.owleyes.org/text/dantes-inferno/read/canto-1