* Air Pressure: Air pressure is the force exerted by the weight of air molecules pressing down on a surface. The more molecules there are, the higher the pressure.

* Water Vapor: When water evaporates, it becomes water vapor, which is a gas.

* Displacement: When water vapor enters the air, it displaces some of the other air molecules (like nitrogen and oxygen). This means there are fewer air molecules in a given space.

* Reduced Pressure: With fewer molecules pushing down, the air pressure decreases.

In simple terms: Think of air pressure like a crowd of people. If you add more people to the crowd, it gets denser and pushes harder (higher pressure). But if you add people who are "invisible" (water vapor), the overall density of the crowd decreases, leading to less pushing (lower pressure).