I've been a creative technology person for almost 2 decades, but node based software is still pretty new to me. In a nutshell, it's a fun and super powerful way to visually program sequences of events to create effects and even entire shows.
People in the effects industry have told me, "a good rule of thumb is go big with nodes or keep it small with layers."
A layer is a singular level inside a layer based software. This singular level can be anything from a video layer to an image. Each effect is also represented individually as a layer. Layers can be combined into bins, directories and groups.
In some layer based applications like After Effects and Photoshop you can nest entire compositions, consisting of layers and groups, into other compositions. Additionally, effects like blur and color correction can be applied to each individual layer.
However, if you want blur and color correction on all layers, you either have to duplicate the effect multiple times or nest it into a new composition. As a direct result of the need for nesting, projects can become quite large, difficult to navigate and unruly.
A node is a singular level inside a node based software. This singular level can be anything from a video to an image to a solid. It strictly models the structural aspect of a system: its behavior is modeled by an explicit relationship to the behavioral concepts.
Nodes in groups are called networks. Nodes can contain their own networks. Effects like blur and color correction are their own nodes.
All you have to do is connect the blur node to the node of whatever you want to blur. If you want something else to have the same blur, just connect the blur to that as well. One change to the blur will affect both nodes if they are both connected.
Unlike layers, you don’t have to change the blur for each layer. This is important for big visual effects shots where you can have anywhere from ten to one hundred nodes or layers. If you decide you don’t like the blur on one node, just delete the connection to that node. The blur will still continue to affect all other nodes.
My brain is accustomed to supporting layer based software and workflows, this is the next shift, thinking in 3D and assigning operators to everything I see. The coolest thing about it is it allows you to "inception" your stuff. You can go in and monkey around with every element within a scene as if it had controls in real life.