Soil is typically used to refer fertile dirt or earth. It is often composed of decaying plant and/or animal matter, particles of various minerals or rocks, and some amount of water in the form of moisture.
Soil is separated into 4 layers called "Horizons".
The top layer is known as the "Organic layer". It consists of decomposing or decomposed organic material. Mostly decomposed plant material such as dead leaves.
The second layer is known as the "Top Soil". This is a largely mineral soil developed from the parent materials. Its dark color comes from leaching off of the organic layer.
The third layer is known as the "Sub soil". This layer is mostly mineral soil with litter organic components. This soil is much more dense compared to the top soil making it more difficult for plant roots to extend downward.
The fourth layer is the unconsolidated material that was once the parent material. Due to it being so far removed from most biological activity and weathering, this layer retains most of the characteristics of the parent material.
Parental material, is the material from which the soil originated. This can range from bedrock, sand, till, or any combination of these materials depending on the region. Over time, erosion and weathering causes larger rocks to brake down into smaller particles and eventually soil.