Composite

The node composites two images together by using a blending mode. It needs two images (or a Constant) as input.

Parameters

Factor: The factor indicates how the two input images are distributed. 0.5 takes both images evenly. 0.0 refers to the first input images and 1.0 refers to the second one.
Operation: The type of blending mode. The different options are normal, darken, multiply, color burn (to darken the image) | lighten, screen,color dodge (to lighten the image) and hardmix, difference, exclusion, subtract, divide.
Fit: How the second image is placed on the first when their sizes differ. contain scales it to fit inside, cover scales it to fill, and stretch ignores the aspect ratio. The output has the size of the first image.