• What is a "mode of production"?
• What is a "social formation"?

"In the Marxist theory of historical materialism, a mode of production (German: Produktionsweise, "the way of producing") is a specific combination of the:

• Productive forces: these include human labour power and means of production (tools, machinery, factory buildings, infrastructure, technical knowledge, raw materials, plants, animals, exploitable land).
• Social and technical relations of production: these include the property, power and control relations (legal code) governing the means of production of society, cooperative work associations, relations between people and the objects of their work, and the relations among the social classes, [JC -- in this case, "social classes" exist]

ref. https://en.wikipedia.org/wiki/Mode_of_production