The bands of different colored or structured materials in some sedimentary rocks are called bedding, stratification, or layers.

Here's a breakdown:

* Bedding: The most general term, referring to any distinct layer in a sedimentary rock.

* Stratification: A more specific term emphasizing the layering of sedimentary rocks, often formed by the deposition of different materials over time.

* Layers: A simple term referring to the individual bands or sheets of rock within the larger bedding structure.

These layers can vary in thickness, composition, and color, reflecting changes in the environment of deposition. For example, a layer of sandstone might represent a period of sand deposition, while a layer of shale might indicate a period of quiet water and fine sediment accumulation.