e-notes Editors are required to answer only one question per request. Please re-list the second part of your question. I will tackle the first one for you.
The setting of a novel refers to both where and when the action happens. Both the historical period and the geographical location of 'Of Mice and Men' assist in expressing the harshness of life for the characters.
Steinbeck chose a location with which he was familiar - the California dust bowl of the 1930's, plagued with the ravages of over-farming and seething with the discontent of labourers rapidly being replaced with advancing agricultural technology. The areas of Salinas and Soledad were known to Steinbeck: he had lived and worked amongst the sort of characters that he created in the novel. These were lonely places,with men constantly moving to keep working and following their dreams. Carlson, Slim, George and Lennie are used to the intinerant lifestyle, and only George and Lennie invest trust in others. Those who stayed did so out of necessity - Candy, Crooks and Curley's wife illustrted these types.