The Massive Allegory
Let’s face it, you can’t really discuss Hell and all its inhabitants without illuminating something about the society that produces such evildoers. So Dante’s personal crisis and journey through Hell could represent every man’s moment of weakness and his descent into sin. This is apparent from the very beginning. The dark woods and night might symbolize man’s sin while the path – which Dante has lost – is the virtuous man’s way of life. The dawn brings hope and the hill crowned with sunlight, which Dante strives to ascend, is the way to God. That his way is obstructed by the three beasts means that Dante is not yet worthy to proceed to Heaven.
Then you’ve got Hell itself, which is basically a microcosm of society. Here, you’ve got all sects of humanity – laymen, clergy, lovers, wagers of war, politicians, scholars, you name it. And they’ve all got their little sections of Hell. Except that all their little flaws are visible to everyone. This is essentially the only difference between the real world and Hell: people become their sins and suffer by them.
That Dante survives Hell, learns from it, and emerges unscathed (read: climbs up into the light) means that he has proven some sort of worth.
The Three Beasts
The leopard, lion, and she-wolf that menace Dante in his quest to get to the sunlight all represent different types of sin. Traditional interpretations have parsed the leopard as a symbol of fraudulence, the lion as a symbol of pride, and the she-wolf as a symbol of avarice or greed. The leopard has few physical characteristics suggesting its interpretation as fraudulence, but the prideful lion has his "head held high."
The she-wolf is described most fully. She "carr[ies] every craving in her leanness," meaning she is painfully skinny. Which explains why she represents avarice or greed. She’s got nothing! But even more interesting is Virgil’s explanation that a Greyhound will eventually come to kill the she-wolf and "restore low-lying Italy." This seems to imply that greed afflicts the whole country. Well, we know that this is true for Florence, given the city’s illustrious textile and banking industry and the political squabbling taking place there at the time. However, nobody can agree about whom the Greyhound represents.