Figurative language uses words or techniques to communicate more meaning than the literal words themselves.

Carver gives the narrator a down-to-earth voice by having him use slang. An example would be his noting that his wife "sent the tapes off lickety-split." "Lickety-split" is slang for quickly. The term adds color and energy to the statement.

Carver communicates the wife's nervousness when the blind man first arrives by using repetition. She repeats the word sofa as she chatters to the blind man:

This is the sofa. We just bought this sofa two weeks ago.

Near the end of the story, when the blind man says "You’re cooking with gas now" he is using a metaphor, a form of figurative language. A metaphor is a comparison that doesn't use the words like or as. The blind man makes this comment as the narrator gets more enthusiastic in his drawing of the cathedral. By likening the narrator's action to cooking with gas he means that Robert is really pepping along, just as a pot on a gas stove might.

The narrator uses another metaphor when he tries to describe the urgency he feels about having to describe the cathedral to the blind man when he doesn't know how. He compares his feeling to:

Say my life was being threatened by an insane guy who said I had to do it or else.

Much of the early part of the story is told relatively flatly, with little figurative language. Therefore, when Carver begins to employ it more heavily, when discussing Beulah working for the blind man, the first effect is that it calls attention to that section, like a special effect. The next effect this more vivid description has is that Carver shares telling details. They make it easy to visualize the situation, which is a commentary on the blindness, and they characterize both those characters described and the speaker.
The next batch of intense figurative language describes the blind man, and again, it both allows us to picture him and tells us about the speaker's character.
Later, the descriptions call attention to the difference between sight and blindness (literal and metaphorical), and later still, when they are drawing, the details and metaphors show the effort made in creating connections.