There are four basic types of clouds: cirrus, cumulus, nimbus and stratus.
Cirrus clouds are high elevation clouds that consist of ice crystals and are about 20,000 feet aboveground. Cirrus clouds are thin and sometimes called "mares' tails". These clouds often indicate a change in the weather.
Cirrus clouds are thin and at high elevation
Cumulus clouds are puffy clouds and are typically present during fair weather. However, these clouds can form towers or strong vertical development. When towers form, watch out for thunderstorms.
Cumulus clouds are light and fluffy
Nimbus clouds are dark -- any cloud that brings precipitation is a nimbus cloud. Expect rain when you see nimbus clouds.
Nimbus clouds are dark rain clouds
Stratus clouds are low clouds. Stratus clouds could bring rain or snow.
Stratus clouds are close to the ground