WIKIPEDIA says:
Conversation is interactive, more-or-less spontaneous, communication between two or more conversants. Interactivity occurs because contributions to a conversation are response reactions to what has previously been said. Spontaneity occurs because a conversation must proceed, to some extent, and in some way, unpredictably.

and WE say:
conversation is like a song. Conversation is and exchange of sounds, dynamics, rythms, musicality, with our without sense. Conversation is a period of time between you and me (and the others).
We talk about what to do, NOW, in this instant moment in front of you and this transforms into a talk about things that cannot be said, unmeaningful vocal sounds, a choreography of missinterpretations. Surfing into the realm of body language, not afraid of being theatrical and personal. Not afraid of talking or dancing to far from what the topic of conversation is. Building a whole realm for imagination.