This service provides a users the ability to choose Sentinel-2 bands for the processing of (Band_A - Band_B)/ (Band_A + Band_B). The default is to use Sentinel-2 Band 8 (Near Infrared) as Band_A and Band 4 (Red) as Band_B (for Sentinel-2 bands see https://earth.esa.int/web/sentinel/user-guides/sentinel-2-msi/resolution...).
The default band values provide the Normalized Difference Vegetation Index (NDVI). The NDVI is a widely used vegetation index that measures the photosynthetic activity and is strongly correlated with vegetation density and vitality. Users can choose every available band combination (see link below).
The Normalized Band Difference service is a parallel processing service based on ESA's Sentinel-2 Toolbox. The Service is labeled "S2_NormBandDiff" and is to be found in the Explorer / Services tab of the Food Security TEP GUI.