The Cheese Man was an enigmatic figure manifesting in the dreams of Buffy, Giles, Xander and Willow following their performance of the Enjoining spell and the death of Adam. He was always seen with cheese slices and making comments about them, hence his alias.
Behind the Scenes
He was portrayed by David Wells.
He was allegedly intended to be the only truly random, chaotic thing in the dreams that otherwise explored the gang's personal fears and failures.
Since Joss Whedon has come out to say that the Cheese Man has no deeper meaning fans have come up with many possible deeper meaning such as "An Analysis of Cheese as Metaphor in Buffy The Vampire Slayer" an article that believes that Cheese is a metaphor for Buffy. Podcaster Alirio from Potentialcast and Redemptioncast believes that the Cheese Man is Joss Whedon him self and he accepts the cheesiness of Buffy but does not let it control him.