How does a biplane work?

Answer 1

Any plane flies by the lift enduced by the air being pulled over its wings, the cross section of the wing is biased so that the air flows faster underneath it than over it (sorry, wrong! The air flows faster over the top because it has further to go (the top of the wing bulges upwards) and this lowers its pressure) and the faster air thus builds up beneath it creating a pocket of higher pressure and pushing the wing upward into the lower pressure pocket above the wing.(the air underneath is at normal pressure, but the air above is at a lower pressure)

The more surface area of the wing, generally the more lift will be obtained, however if the wing extends too far along the plane's length then it will hamper the steering/control of the plane, if the wings extend too far away from the fuselage then the supporting beams needed to stop the wings from snapping off would become to heavy.

the remaining option for increasing the lift via wing surface area is simply to add another wing making a biplane, the second wing's height and position above the primary wing is critical as too close and the air producing the lift from the upper wing would press against the lower wing ruining the aerodynamics of both and producing no lift. too far apart and the structures to hold the wing that high would become a hinderance and a weight issue. although there were Triplanes that flew fine, unfortunatly after too many wings are added the whole thing becomes unstable and folds in on it'self though this didn't stop many Victorians from trying and failing.

But in simplified form: the biplane works by increasing the lift of the wings for minimal extra weight from supporting structures, as well as keeping the centre of mass more central than an extended wing design.