These e-courses introduce the European soil types according to the World Reference Base for soil resources. WRB is a two-level system of soil classification with 30 Soil Reference Groups and a series of uniquely defined qualifiers for specific soil characteristics.

For describing and defining soils the WRB exploits the following nomenclature:

• soil characteristics comprise single observable or measured parameters;
• soil properties are a combination of characteristics indicating soil-forming processes;
• soil horizons represent three-dimensional bodies containing one or more soil properties