The horizontal layers that are typical of sedimentary rocks, known as strata or beds, are formed through the process of sedimentation. Sedimentary rocks are formed when sediment, such as sand, mud, or gravel, is deposited and compacted over time. As new layers of sediment are deposited on top of older ones, they form distinct strata. These layers can vary in thickness, grain size, and composition, reflecting changes in the depositional environment over time.

On the other hand, the bands featured in metamorphic rocks, known as foliations, are formed due to the process of metamorphism. Metamorphic rocks are formed when pre-existing rocks undergo changes in their mineral composition and texture due to heat, pressure, or both. During metamorphism, the original minerals in the rock recrystallize and align themselves in a preferred orientation due to the influence of directed pressure and heat. This alignment creates bands or foliations that give metamorphic rocks their characteristic layered appearance.

Foliations in metamorphic rocks can vary in their spacing and distinctness depending on the degree and type of metamorphism. Some common types of foliations include:

- Slaty cleavage: This is the finest type of foliation, where minerals such as mica and chlorite align to create closely spaced, thin, and parallel layers.

- Schistosity: This type of foliation is coarser and more pronounced than slaty cleavage, with larger crystals of minerals like mica and amphibole aligned in parallel layers.

- Gneissic banding: This is the coarsest type of foliation, characterized by alternating light and dark bands of different mineral compositions.

In summary, the horizontal layers in sedimentary rocks are formed through the deposition and compaction of sediment, representing changes in the depositional environment. On the other hand, the bands in metamorphic rocks are formed through the recrystallization and alignment of minerals during metamorphism, reflecting the influence of directed pressure and heat.