If one makes a comment, another asks a question, and a third makes a suggestion, then a discourse exists which may be considered a conversation, exchange, dialogue, or discussion, all words which are synonyms of each other and may be used interchangeably in common usage.
I liked the three-car garage and wouldn't be embarrassed to park any of my cars there . . . might even be able to fit one or two more without crowding, since most of my cars are on the small side ;^)