The best way to answer this question is to give an extended quote of a refrain in the book. George and Lennie have a dream or vision to have a small plot of land. On that land, they will have a small house and grow their own vegetables. They will also have rabbits for Lennie to tend. They won't have to travel and live a life filled with hardships. The vision is akin to a land flowing with milk and honey, a veritable Promised Land for migrant workers on the road.
Here is the quote:
“O.K. Someday—we’re gonna get the jack together and we’re gonna have a little house and a couple of acres an’ a cow and some pigs and—"
“An’ live off the fatta the lan’,” Lennie shouted. “An’ have rabbits. Go on, George! Tell about what we’re gonna have in the garden and about the rabbits in the cages and about the rain in the winter and the stove, and how thick the cream is on the milk like you can hardly cut it. Tell about that, George.” “Why’n’t you do it yourself? You know all of it."
“No . . . . you tell it. It ain’t the same if I tell it. Go on . . . . George. How I get to tend the rabbits."
“Well,” said George, “we’ll have a big vegetable patch and a rabbit hutch and chickens. And when it rains in the winter, we’ll just say the hell with goin’ to work, and we’ll build up a fire in the stove and set around it an’ listen to the rain comin’ down on the roof...”
The is one of the beautiful passages in the book, because no one dreams. Steinbeck's world is a world without dreams, because all of them have been shattered. Therefore, Lennie and George stand out. They dare to dream and labor for it.
The language they use is the diction of hard working men, who have not had the privilege of education. The grammar is not correct, but it is filled with hope add courage.