Describe the relationship between George and Lennie. What does each gain from the relationship?

Within the context of the novel, the relationship between our two protagonists is indeed unique. George states in chapter one that, as far as relationships go, he and Lennie share something special. Unlike other ranch hands who come to a ranch, work up a stake, spend their wages, and soon find themselves on another ranch, he and Lennie

"got a future. We got somebody to talk to that gives a damn about us. We don't have to sit in no bar room blowin' in our jack jus' because we got no place else to go. If them other guys gets in jail they can rot for all anybody gives a damn. But not us."

Lennie is quite proud of what they have and supports George's sentiment by mentioning that

"I got you to look after me, and you got me to look after you, and that's why."

It is this aspect of their relationship that makes the two men different from others. They care for one another and share a dream, which is lacking in the other men. George further proclaims that

"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—"

Lennie excitedly says that they will "live off the fatta the lan'," meaning that they will own property one day and enjoy its produce. They will not be reliant on anyone; they will have achieved independence. Their destiny will be in their hands. Lennie wishes to tend rabbits once they have reached their goal, and George agrees that Lennie will have as many rabbits as he wants.
The two men are proud of their close friendship. George, who is the more intelligent partner, makes all the crucial decisions and decides where they should work. Lennie is a mighty hunk of a man and can do the work of many men. The two have arguments now and again when George expresses his frustration about Lennie always getting them into trouble. This happens because of Lennie's intellectual limitations and his inability to understand and control his strength.
In spite of these disagreements, it is apparent that the two men care deeply about one another. George has made a promise to Lennie's aunt Clara that he will look after him, and he has done that with aplomb. At the end of the novel, he, for example, takes the ultimate step in securing Lennie's dignity and safety by shooting him before Curley and his men get to him. George realizes that they would torture Lennie before finally killing him. His desperate act indicates the depth of his love and care for Lennie.
It is ironic that the two men's dream is shattered by Lennie's unfortunate inability to control his strength, for it is his power that George uses as a selling tool whenever they arrive at a new ranch. Further irony lies in the fact that after Lennie's death, George finds himself in the same position as all the other ranch hands: his dream is in ruins, and he is without a confidante.