What is not for nothing meaning?

"Not for nothing" is an idiomatic expression used to indicate that something should not be taken lightly or dismissed, and that there is a good reason or justification for it. It is often used to emphasize the importance or validity of something by suggesting that it is not merely a meaningless or insignificant statement. For example, "I didn't spend all that time studying for nothing" means that there was a purpose or goal behind the studying, and that it was not a waste of time.