Boolean
The Boolean node produces a boolean value, that is, a value which can be either true or false (you can also think of it as on or off).
Bellow is a screenshot of the node and of its inspector panel. You can use either one to set the node's boolean value.

Inputs and Outputs
Inputs:
Value: a boolean value.
Outputs:
Output: a boolean value.
Example
In this simple example we use a boolean node to toggle between a small blur radius and a larger blur radius:

