Hint: Air pressure is the pressure exerted by the weight of air on the earth’s surface. Air pressure is measured with a barometer. The tighter the air molecules are packed together, the higher the pressure. Air pressure is affected by temperature, altitude, and moisture.
Complete answer: The moon is the celestial object that orbits our earth and is it’s only natural satellite. Like earth, the moon is made of rocks and metal. Our Moon doesn't have an atmosphere because of its size. It is too small to have a strong magnetic field of its own. Since there is not a strong gravitational pull acting on the surface of the moon, the value of acceleration due to gravity on the surface of the moon is negligible. Due to this phenomenon, all the molecules and gases are absent, meaning the moon has no atmosphere. Air molecules have some weight, and the large numbers of air molecules that make up the layers of our atmosphere altogether have a great deal of weight, which presses down on anything that is below it. Therefore due to the lack of air molecules, and an atmosphere, the moon has no air pressure either.
Note: The moon has a very thin layer of gases on its surface, however this layer is negligible and therefore should not be confused with the atmosphere as this thin layer of gases does not constitute an atmosphere.