Jessta Roll

“The primary uses of monads in functional programming are to express input/output (I/O) operations and changes in state without using language features that introduce side effects^[3]. They exploit a loophole that, although a function cannot directly cause a side effect, it can construct a value describing a desired side effect that the caller should apply at a convenient time. However, I/O and state management are by no means the only uses of monads. They are useful in any situation where the programmer wants to carry out a purely functional computation while a related computation is carried out “on the side.”“

I read the words, but what do they mean in reality?