There are three main types of nodes in DaVinci Resolve:
- Layer Mixer
Serial nodes work in a linear fashion with the output of each node feeding the input of the next node in the chain.
Parallel nodes allow you to "apply two or more overlapping adjustments at a single stage of a node tree." Which is possible because it has multiple RGB inputs but a single RGB output. This means the order of the corrections within the group is irrelevant.
Layer Mixer nodes are similar to Parallel nodes except that priority in the mix is given to the 'image adjustment in the lowest overlapping node input" and you can combine all of the corrector nodes using "one of several different composite modes." This enables you to adjust how they behave when mixed together.
(You can read more about this on page 2,810 of the Resolve 17 manual.)
Now let's see a much better explanation of what's actually happening...