Context is the "setting" in which society has its certain values and attitudes. It is the combination of all the factors which influence the values/attitudes of society/the individual. Thus, context encompasses the time period, culture, location, major events (especially political), etc., etc. of the text.
Eg: One of the beliefs society has about women in the 18th century England (the context) is that women are not as good as men (the value). Therefore, their treatment of women is inferior to their treatment of men (the attitude).
However, in the 21st century (the context), society believes that men and women are equal (the value) and treat thems as such (the attitude).
Context also varies depending on the culture. An African person will have different values and attitudes to an American because of their culture/the way they were raised.