Have you ever played with a dirt clod? A dirt clod is a small clump of soil that has formed a rock-like clump. These dirt clods are called peds by geologists.
Many soils form peds as soil fragments bond together. These peds affect how easily water is able to move through the soil, as well as plant roots and other organisms.
Peds tend to form more often in wet locations, and less frequently in drier locations. Sandy locations, such as deserts, do not form any peds at all.