The Platonic dialogues are the writings in which Plato lays out his philosophy. They are called dialogues because they are written as a series of conversations as opposed to simple treatises on philosophy.
In these dialogues, Plato himself is never "present." Instead, the dialogues feature some teacher (typically Socrates) is having a discussion with some person about a particular philosophical issue. Because of this, we do not really know how the extent to which the ideas presented in the dialogues are those of Plato. They may well be a mix of Plato's own ideas and those of Socrates or others.
The Platonic dialogues, then, are a series of philosophical works written in the form of dialogues between two or more people.