The word "upper" is an adjective that means higher or highest. It’s almost always used in front of a noun. The opposite of "upper" is "lower."
The leftover food is on the upper shelf in the refrigerator.
The store you’re looking for is on the upper level of the mall.
The upper classmen at the school, the juniors and the seniors, have certain privileges that the other students don’t have.
She has sort of an upper-class accent.
They consider themselves to be in the upper-middle class.
Who do you think has the upper hand in this situation? (upper hand = advantage)
The rooms on the upper floors of the hotel are not as nice as those on the lower floors.
The houses in this upper-income neighborhood sell for well over a million dollars each.
The elevator will bring you to the upper levels
of the building.
Note: When describing a person’s rank in society, it sounds better to say "upper income" instead of "upper class." The same applies to descriptions of people in the "lower income" areas of society. Try not to say "lower class."