Cis means same as opposed to trans which means opposite it’s commonly used to describe the shape of molecules in chemistry but is also used to say if a persons birth sex is the same (cis) or different (trans) then their gender

Het is short for hetero which means different vs homo which means the same so if you had homogenized milk it’s all uniform and the same vs a heterogenous mixture which would have some areas of extra fat. Those are used as hetero and homo sexual where a homosexual likes people of the same sex and heterosexuals like people of the opposite sex

So a cis het male is a dude whose not trans who likes banging chicks