George and Lennie are both migrant workers eeking out a living as farmhands in California during the 1930's. They live in constant precarity and as drifters they are unable to settle down and "belong" anywhere.
George has known Lennie since childhood and has taken on the responsibility of looking after Lennie ever since his aunt died. They are friends by circumstance, but their friendship goes deeper than just that. Unlike other migrant workers, George and Lennie have each other to count on; they are "family."
This is why their dream of owning and running a small farm is so important. As much as financial security, George and Lennie need each other's companionship and roots.
Although they both want to live off the "fat of the land," these two characters are foils of one another. George is smaller in stature, but he is street smart. Lennie, on the other hand, is physically gigantic but is child-like in his mannerisms and his mentality. Despite these sharp contrasts, they both yearn for peace of mind where they can work their own land with their own hands.