Symbolism, Imagery, Allegory
We’re close to Heaven, so what do you think of when you see wings? Angels? Good call. Lots of the wing imagery occurs around appearances of the angels. The wings signify the angels’ superhuman status. They can fly! We humans have nothing to rival that.
Indeed, wing imagery is often used to counter foot imagery. Get it? Walking versus flying? How does that work? Well, remember that when each of Dante’s P’s is removed from his forehead, his feet suddenly get lighter and he feels as if he can fly up to the next terrace? The wings—imaginary as they are—signify a lightening of one’s load and a resurgence of eagerness to climb faster to get to the top of Mount Purgatory.
At the most basic level, wings represent the ability to get closer to God. And this is exactly how they function for Dante. When each of the P’s on Dante's forehead is erased, the "eraser" is an angel’s wing. The brushing away of the letter means an easier and faster ascent to God. Whether physically or metaphorically, they speed up Dante’s ascent and whisk him up to God faster than his mortal feet, weighed down by the burden of sin, ever could.