How Many Types of Clouds Are There?
There are three major types of clouds.

Stratus Clouds

These clouds stretch across the sky. They look like fog and often produce drizzle. They are low-level clouds. stratus.jpg

Cumulous Clouds
These clouds are puffy clouds. You see these on a beautiful day. They are made from water droplets. They are mid-level clouds.

Cirrus Clouds
These are feathery and milky clouds. They are formed from ice crystals and tell us when a storm is coming. They are high level clouds.

Cumulonimbus clouds are thunderstorm clouds. High winds can flatten the top of the cloud into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning and even tornadoes. The anvil usually points in the direction the storm is moving.
Nimbostratus clouds form a dark gray, wet looking cloudy layer associated with continuously falling rain or snow. They often produce precipitation that is usually light to moderate.
Stratocumulus clouds are low, puffy and gray. Most form in rows with blue sky visible in between them. Rain rarely occurs with stratocumulus clouds,however, they can turn into nimbostratus clouds.
Altostratus clouds are gray or blue-gray mid level clouds composed of ice crystals and water droplets. The clouds usually cover the entire sky. In the thinner areas of the clouds, the sun may be dimly visible as a round disk. Altostratus clouds often form ahead of storms with continuous rain or snow.

Why are clouds white?

Not all clouds are pure white, however, for those that are white it is due to their altitude and the reflection of the sunlight.

Clouds are white because their water droplets or ice crystals are large enough to scatter the light of the seven wavelengths (red, orange, yellow, green, blue, indigo and violet) which combine to produce white light.

Clouds will appear dark or gray when either they are in another clouds shadow or the top of a cloud casts a shadow upon its own base.