Here's what defines it:

* Parent material: This horizon is primarily composed of the partially weathered bedrock or geological material from which the soil developed.

* Little to no organic matter: Unlike the upper horizons (A and B), the C horizon has very little organic matter.

* Less weathered: It's less weathered than the horizons above it, meaning the original rock structure is still relatively intact.

* Transitional: It often acts as a transition zone between the bedrock and the overlying soil.

Here's a simple analogy: Imagine building a house. The C horizon is like the foundation, the bedrock that supports the structure. The A and B horizons are like the floors and walls built on top.

Important Note: Not all soils have all three horizons. Some soils may have a very thin or absent C horizon, especially if they are young or formed in a highly weathered environment.