It strongly depends on your background. What kind of programs are you writing? If you have a lot of boilerplate for error handling, creating chains of promise

It strongly depends on your background. What kind of programs are you writing? If you have a lot of boilerplate for error handling, creating chains of promises or passing a file handler to log to around, that's the kind of thing monads can help abstract away (from a programming point of view). They are a more general construction in category theory but knowing that doesn't tell you how to use them (because the full generality is not often needed).