The word dialogue comes from the Greek meaning to converse with one another, or to meet together with one another. In examining the kind and character of each Platonic dialogue, we proceed as biologists in dissecting contents to reveal the form of the dialogues.
In the first place there are two kinds of Platonic dialogues, narrated and performed. A narrated dialogue is one in which people are recounting, or recalling, the scene of the dialogue. It serves as a kind of introduction and there are nine narrated dialogues, with six narrated by Socrates. An example of a narrated dialogue is the Theaetetus. A performed dialogue simply begins en media res without an introduction and is the most common type of Platonic dialogue as there are twenty-four performed dialogues.
A second division is between Socratic and non-Socratic dialogues, wherein Socrates is the chief speaker. In the vast majority of dialogues (twenty-eight) Socrates is the chief speaker. An example of a non-Socratic dialogue is the Laws or the Sophist.
Third we notice the large number of proper names that serves as titles of the dialogues (twenty-seven of thirty-five). Elsewhere in ancient literature we find proper names as the titles of tragedies (Oedipus or Antigone), however in the Platonic dialogues the proper names are of contemporaries not heroes. The Platonic dialogue is some kind of a harmony between the tragic and the comic (see the end of the Symposium). In only four dialogues does the title reveal the subject matter: Republic, Laws, Sophist, and Statesman.
Lastly, the setting and the characters. All of the dialogues occur within Athens, excluding the Laws (and its debatable sequel the Eponimis). However, the Phaedrus occurs outside the city walls of Athens and the Republic takes place down the harbor of the Piraeus. In no dialogue does Socrates speak with a common worker -a laborer, artisan, blacksmith and so on, despite the fact that he is always considering them and in the Apology he identifies them as people he engages with.
As has been said, one of the central problems with writing is that the text is universal and equally shared among all people. That is, the writer must speak to everyone on an equal standing. However, the Platonic, in its deliberate ambiguity and obfuscation, is an attempt to overcome this problem of writing -that is, to transcend the finitude of the passing moment, while preserving the esotericism of the teaching.