The clouds in the sky are formed by water vapor, which are tiny drops of condensed water. These water droplets are to small to precipitate but they are big enough to form a cloud. Most water vapor that makes up a cloud doesn't fall as precipitation because it is too small. In order for the water droplets to fall, they have to stick to other water droplets and expand. If enough water droplets collide and a droplet forms that exceeds the fall velocity then it is considered precipitation. It is no ta easy process because you need millions of water droplets to make one efficient one.
Precipitation
rain, snow, or hail, all of which are formed by condensation of moisture in the atmosphere and fall to the ground