The poem does not explain: it says that Dante, midway along the path of life, found himself in a dark wood, because he left the straight way without knowing when, and that a leopard, a lion and a she-wolf block his climb toward a hill lit by the sun. The meaning of each image comes from the readings the commentators made afterward.
About the wood, the text says only that Dante cannot tell well how he entered it, so full of sleep was he when he abandoned the true way. It speaks of fear, of a night spent in such pain, and of the sun which, at the top of the hill, calms the anguish. Two readings coexist: distraction without fault, because no one deceived him, or sleep as failure, because the poem points to no other cause.
Of the three beasts, only the she-wolf has its meaning stated by someone, and it is Virgil who states it: she is of so evil a nature that she never satisfies her desire and, after feeding, is hungrier than before. She will die only when the Veltro comes, the deliverer who will feed on wisdom, love and virtue. Of the leopard and the lion the poem says nothing; the readings that assign them sins, for example the three great categories of Hell, incontinence, violence and malice, come from tradition, not from the verses.
The Veltro is never named. Virgil says only that he will be born "between felt and felt," and the expression is left without solution in the text.