After a military coup creating the Republic of Gilead from the once powerful United States of America, inhabitants find themselves in a strict, domineering caste system based on the hell, fire, & brimstone from the Old Testament of the Bible. They believe that all their problems (rampant infertility, land deterioration, and an amoral society) can all be solved by returning to their close-minded roots.
What this means in practice for the men and women of Gilead is a complete overhaul of their social hierarchy as they know it. Now, your place in society is determined by your rank within the new infrastructure and the power you wield. Women are even lower in this caste system, as dictated by the ruling body and their twisted sense of ideology, and are subservient to the male figure in their life. While this isn't necessarily awful for most women, for those who belong to the "handmaid" class it is a nightmare. They are used for breeding purposes only, as if they were an animal.