When writing script you could code something that will fail in certain circumstances.
By default Flow will handle errors in your scripts by logging as much information as possible to the action Log. This is normally enough for most situations however occasionally you might require to handle the error yourself and provide custom logic.
The See "Try...Except" statement can be used to provide custom error handling logic. Instead of the standard error message being written to the Log you can write a custom error message. Otherwise instead of an error message you could provide script to set the field to a different value using a different calculation.
The See "Exceptions" functions are used within the Try...Except statement to capture information about the exception
Try...Except statements can be nested within each other to provide for multiple alternatives when failures occur.