Expression

An expression node contains any arbitrary GCScript expression.

It is the type of expression you write into an input port, except it is extracted as its own node for clarity so its value can be input into multiple input ports.

Extracting expression into itself creates new Expression node in the input port wire

There are several ways to create an expression node:

From the Node Types dialog.
By right-clicking on any input port and choosing Extract Expression Into its Own Node.
Within any input port, type a value of the form "name=expression". This creates a new expression node with the given name and expression.

The Reinitialize Expression option detaches the wire from the new expression node.