Object Oriented Programming

Yeah re-useability is what I always hear but isnt that the same case for functions?

Also I hear OOP helps organise your code better but I dont like it when a file has something like 6 long functions in it and you have to struggle scrolling through the file to find something which can be the case with classes.

Isn't having a class effectivly like having a function that will run through some sub functions and then finally return an array.