NDVI equation is expressed as NDVI = (NIR – red) / (NIR + red). From the equation, we can see that NDVI intends to see the normalized difference between NIR and red spectrums. A higher difference or higher NDVI means that the object in the pixel is more likely to be vegetation, such as forest and crop. Lower NDVI value means that the object can be other objects, like water, soil, settlements, cloud, or shadow.