The validator node can be used to implement all kind of validations required as part of task execution, to confirm if a step has happened or not, to do an action performed on that or to check if the execution is progressing as planned.
Multiple levels of complex validations rules can be added using constant values/Variables/expressions using different operators like =,!=,<,>,<=,>=,like, AND,OR etc.
By setting the toggle button - ‘Stop on validation error’ to ON in properties, the further execution of the task can be controlled.