High clouds are anywhere from 5,000m-13,000m high. Some examples of these kinds of clouds are cirrus and cirrocumulus. Contrails are also included in this altitude.

Middle clouds are located anywhere from 2,000m-7,000m high. Examples of these clouds are altocumulus and altostratus.

Low clouds are located from the surface up to 2,000m. Examples of these clouds are cumulus and cumulonimbus.

Cloud height depends on factors such as region.

There are also clouds located in the stratosphere and they are called polar stratospheric clouds. The mesoshpere aslo has clouds called polar mesoshperic clouds.

The lowest level of clouds are "stratus" clouds that often fill the entire sky but rarely drop precipitation and are often similar to fog.  Nimbostratus clouds are slightly higher and do often drop light precipitation.

The next level includes Altocumulus which are grey and puffy and often signify thunderstorms on the way and Altostratus clouds that fill more of the sky and are often thin enough to allow the sun to shine through dimly and produce steady precipitation.

The higher clouds are usually Cirrus clouds, thin and whispy, generally you see them when the weather is really nice.  They are often at or above 20,000ft making them truly "high" clouds.