Answer:
Crooks is sitting in his room when Lennie comes by. They're alone, because everyone else has gone off to Suzy's clean and comedic house of ill repute. Lennie (revealing his secret-keeping capabilities) immediately tells Crooks about the dream farm. Crooks is a character used by Steinbeck to show the effects of discrimination. Chapter 4 begins and ends with Crooks putting liniment on his back in his room. He's isolated from the rest of the men and pretty much stays to himself in his room when he isn't working. He stays in his room when he isn't working because he is a black man and at that time, when all the other ranch workers were white males, Crooks was discriminated against because of his race.
Steinbeck teaches us about the way black people were discriminated against and the American dream. This is the idea that in America, it is possible for anyone to achieve success and improve their lives through hard work. This is linked to the United States Declaration of Independence which states that 'all men are created equal'. In chapter 4 we learn about everyone's dream and how it is all linked in with the American dream.