Hi J,
Yes, the XPresso is on a Null to keep it movable. The Object manager position defines part of the priorities. Besides, Xpresso can have absolute and relative positions, making it easier to exchange objects later on. But placing it on an object is fine as well.
Think of the Noise node like the Landscape object. It is pretty much a noise-based displacement. When you change slowly, the scale is similar to the virtual noise node results are visible.
This landscape has a reporter sitting there and reporting every frame the current elevation of this specific location. That is the output of the noise node.
The random (noise) results will provide a number that the Altitude value (Amplitude) limits. In short, the light constantly flickers as it changes between 0 and 1.
With the Compare, we ask now, is it bigger or smaller? Yes or no (1 or 0) is the answer. Light goes full on or off.
We could also use this 1 or 0 to feed in each time something different; we use the Condition node.
So if there result is 0, then the first input of the Condition is used. If it is 1, then the second input.
You wanted to have it primarily on, with flickering interruptions. So, input one is set to 100% (or 1).
When the flickering should happen, we use input two of the Condition, and there we feed another noise with a different Seed and other settings in. (so we can adjust this independently).
With Color, we split the flickering and adjust its value in Red, Green, and Blue values (XYZ, via a Range-Mapper. This allows us to increase the value for Green, for example, a little bit earlier. Or, for a light bulb, the orange tone will stay longer than the cold parts of the light.
Here are the color examples
https://www.amazon.com/clouddrive/share/WO70x8EH3qVC9oAVkErGdm9b7KhLx5DFOJ99fMWrYc8
In your example the Amplitude is 3.5 and the “switch between 1 and 0 happens at 1.99. I use sometimes larger numbers to make it clear, or to get for the 100% more hits.
The input2 parameter of the Condition is set to 2, which delivers a value for the light of 200%. At the same time, the flickering for the light itself is between 0-350% in your example.
Note that the values to trigger the Condition are independent of the values you feed into it.
Enjoy your long weekend (if you are in the US.)