Normalised Difference Vegetation Index (Rouse et al., 1974).

It is one of the first SVIs which was introduced to monitor vegetation (from Landsat 1) and over the years it has been widely used to estimate parameters such as e.g. Leaf Area Index, biomass, and fractional vegetation cover.
The index span from -1 to 1, with healthy vegetation usually occurring for values >= 0.5. Values below that threshold often indicate overgrazed or unhealthy pasture lands.

The output image is masked to include only the pixels within the pasture areas, irrespective of NDVI value.
Pixels whithin pastures that correspond to cloud shadow in SCL product are re-valorized to -1.5, while pixels corresponding to clouds and thin cirruses in SCL product are re-valorized to -2.

The index formula is defined as:
(B8A - B4) / (B8A + B4)