Wing Loading is the details of the distribution of pressure on an aircraft wing. An aircraft flys by producing Lift by its wings. This lift force depends on the shape of the wing that produces high pressure on the bottom of the wing and low pressure on the top. The center of the lift is usually at the 1/4 chord or 25% of the width of the wing as measure from the leading edge.
The Wing Loading can be designed to produce different Lift and ensure the aircraft will be easy to trim for level flight.
In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly, the landing and take-off speeds will be higher. The high wing loading also decreases maneuverability. The same constraints apply to birds and bats.