Air can move.  Moving air is called wind.  

Air is a gas.  We breathe air.  Air is part of the atmosphere around the Earth.

Air can push down towards Earth.  This is called air pressure.  pressure means to push on something.

A day with a lot of moving air is called a windy day.

Sometimes air moves, but lightly.  This is called a light wind.

Sometimes air can push very hard.  This is called a strong wind.

There are things that measure weather.  A barometer measures air pressure.  A barometer measure how strongly the air is pushing down onto the Earth.

Measure means to find out how much of something.  We can find out how light, how heavy, how strong or weak something is.  We can find out how hot or cold, or long or short something. is. We can do this by meauring it!