The values that flow from node to node in the graph are Node Values because these values are generated by the node and they live in the node.
There are 7 node values:
A boolean value. (true or false).
In Wiki:
Type: BOOLEAN
Value: true
A real number value. (0.0, 3.0, -2.0, 5.4, 3.141592).
Example in Wiki:
Type: NUMBER
Value: 2.54
A 2D point or vector value ([0.0, 0.0], [1.0, -3.0], [2.4, 3.8]).
Example in Wiki:
Type: POINT
Value: [2.6, 3.8]
A rectangle defined by a position and size. (pos:[0.0, 0.0]; size:[120.0, 100.5]).
Example in Wiki:
Type: FRAME
Value: position: [5, 3] - size: [120, 100]
A red, greed, blue and opacity value. ().
Example in Wiki:
Type: FRAME
Value: red: 0.25 - green: 0.5 - blue: 0.85 - opacity: 0.95
An image value.
Example in Wiki:
Type: IMAGE
A Bezier Splines container with multiple curves.
Example in Wiki:
Type: CURVES
A procedural texture definition.
Example in Wiki:
Type: TEXTURE
The Attributes node can hold custom attributes and convert them to Node Values. With this feature you can reuse attributes through the project.