Those rules will make writing dialogue easy - turning it from something static, heavy and unlifelike into something that shines off the page. Better still, dialogue should be fun to write, so don't worry if we talk about 'rules'. It takes time to develop a good ear for dialogue, but following some simple rules and avoiding some obvious pitfalls can make a huge difference.
It solves the story's problems, sketches in clues, builds ... dialogue can be considered as a free flow of meaning between people in communication, in the sense of a stream that flows between banks. These "banks" are understood as representing the various points of view of the participants. Dialogue is a contraction from the Greek words for through and words.