This generator is used to combine several maps so that their sum is always 1.
Normalize Generator final result depends on the layer order. Layers are blended together similarly to the layer system in Photoshop and other graphics editors: Each of the upper layers overlaps the lower ones. A mathematical algorithm for each layer generator multiplies all underlying layer values with the inverse value (1-value) of the current layer. The sum of the output maps values is always equal to 1.
Some generators like Biomes Set or Textures Output have a normilizer built-in, but in some cases it would be handy to pre-normalize them manually. In other cases it would be necessary to normalize masks for Mask node, Grass Output or other nodes.
Input in all of the layers - source non-normalized maps.
The Background layer does not require an input since it is regarded as completely filled (a constant of 1). This layer could not be removed or sent up or down.
Map outputs in all if the layers - input maps processed so that any pixel sum of the map values is equal to 1.