This node simply calls the C# String.Format function using the provided parameters. It allows you to take a string like "I am a {0} who likes to do {1} while {2}" And populate {1}, {2}, and {3} with values. If you plug any value into the list of inputs for the Parameters, it will auto add a cast node into an object.
For example using the string "The number {0} is on the {2} hand and the fact it's enabled is {3}." for Format. Then Plugging in a float (1.25) for the first input, Then a Chirality (Left) to the second, then a Boolean (True) will result in the output "The number 1.25 is on the Left hand and the fact it's enabled is True."
Inputs
Format (String)
FormatProvider (IFormatProvider)
An object that supplies culture-specific formatting information.
Nodes that output this type can be found in Strings/Localization
Outputs
* (String)
The formatted string.