Just because a character says something, it doesn't become dialogue. Dialogue is about demonstrating character through conflict. Dialogue is the function of the character in a drama or a theatre.
Dialogue is just another way of getting what a character wants. When characters talk, they do it for a reason, consciously or unconsciously.
Dialogues are a very useful tool in theatre. Not only do they give voice to the characters, but they are also helpful at many other levels.
A major feature of dialogue is that it moves the story forward in a more straight-forward way than a narrator’s explanation would. What characters say leads to something happening in theatre. Through dialogue, a decision is made, a question is raised, information is released, or tension is built. Even silence forwards the story.
Characters can also evolve through dialogue. In fact, in every good dialogue, at least one of the characters should undergo a change of mood. Choice of words, unique syntax,and mannerisms in dialogue reveals much about a character.
Dialogue provides information that the reader senses (often unconsciously) about the relationship between the characters, their personalities, and their moods, etc. Apart from that, it gives specific data about the plot, so all of the information provided in a dialogue must be justified. Characters generally don't exactly say what they mean. But through the subtext provided in their dialogue, audience can understand the meaning.
Good dialogue engages audience and entertains them.
Writing good dialogue is a hard task. It takes practice and patience. Here are ten tips for you to improve how you write your dialogue so your conversations crackle on the page.
V.O. (voice over) and O.S. (off-screen) are similar terms, but they have slightly different applications. Both are used to indicate that dialogue is spoken by someone not currently seen on the screen; the difference isn’t where the speaker is not, but where the speaker is.