When the value of something you're buying is higher than the cost, you say that it's "worth the money". Here's an example:
This coat was pretty expensive, but it's definitely worth it.
You can also use "worth ___ing" when you're talking about whether the value you get from doing something is higher than the money, time, and work that it takes. Like when you go to see a movie, it costs money and takes up a few hours of your time. So people often ask their friends questions like:
Would you say it's worth seeing?
Use the phrase "it's not worth ___ing" to talk about an action that wastes time or money, and isn't enjoyable. In the example at top, the speaker says "it's not worth entering" because he feels that he won't be able to win, so entering the contest will only cost money and time.