The major difference between talking and communicating is that communicating is a two way process whereas talking is a one way process. Let us look at two important ways in which this is so.
First, communicating involves listening where talking does not. If a person is truly communicating with another person, they must care what the other person thinks and what the other person has to say. In order to understand what the other person thinks, the first person must listen. More than that, they must try to understand what the other feels. This involves paying attention to body language and nonverbal communication. It also involves trying hard to understand what is being said both explicitly and implicitly. Talking does not involve any of these things.
However, communication will require a person to talk. When the person does talk, the second important aspect of communication comes into play. The second aspect is that the things that you say when you communicate have to be informed by what you understood and learned when you were listening. If you are communicating, you have to respond to what the other person has said or otherwise communicated to you. If you are just talking, you deliver your message without any thought as to what the other person’s message to you.
Thus, communicating is a two way process in which a person truly works to understand their interlocutor and then structures their own messages around what they have learned.