Here's a breakdown:

* Shape: This refers to the general appearance of the cloud, and is used to categorize them into three main types:

* Cumulus: These are puffy, cotton-like clouds.

* Stratus: These are flat, layered clouds.

* Cirrus: These are wispy, feathery clouds.

* Altitude: This refers to the height of the cloud above the ground, and further divides the main cloud types into different levels:

* High-level clouds: These are found above 6,000 meters (20,000 feet) and are mostly made of ice crystals.

* Mid-level clouds: These are found between 2,000 and 6,000 meters (6,500 and 20,000 feet) and can be made of both water droplets and ice crystals.

* Low-level clouds: These are found below 2,000 meters (6,500 feet) and are primarily made of water droplets.

By combining these two factors, we can create a more specific classification system for clouds. For example, a "cumulonimbus" cloud is a towering, puffy cloud that reaches high into the atmosphere and often produces thunderstorms.